Sho in canon
When he initially transformed into the Guyver, Sho was unconscious from the trauma of having the Unit forcibly bond itself to him. However, the Guyver itself was able to deal with the threat of the Zoanoids that had been dispatched to retrieve the lost Guyver Unit. Once Sho awakened from the fugue-like state that he had entered while bonding to the Unit, he was initially terrified of the armor that he found himself wearing, as well as its capacity for sheer destruction.
These feelings lead to him rejecting the armor, which in turn caused the armor itself to retreat from him and store itself in the sub-dimension that the armor resides in when not in use.However, this was only a temporary reprieve; the armor itself was still firmly bonded to him. Nothing short of the Unit Remover would be able to change that fact. Sho, however, was simply relieved to be free of the armor; he didn't know yet that he would not be able to get out of the situation so easily.
When the next group of Chronos thugs confronted him - a pair of Ramotith lead by Guyver II in the 12 part OAV, and a group of Ramotith lead by a Vamore in the 2005 TV series and the manga - he was again able to call upon the Guyver to protect himself and his best friend, Tetsuro. In doing so, he discovered the most powerful of the Guyver's weapons: the mighty Mega Smasher; in the first two OAVs, he was also able to kill Guyver II at this point.
After that, Sho began to realize that the situation he was now in was very serious, and also, that there was far more to it than what he had seen so far.
From there, the stories follow two divergent, but related, paths.
In the manga/12 part OAV
Lisker, having had extensive combat training as part of his pre-processing preparations for becoming a Hyper Zoanoid, was easily able to get the upper hand on Sho. However, due to a timely malfunction on the part of Lisker's Control Medal, Sho was able to gain back the upper hand and kill him on the very same day he made his attack on the high school Sho, Tetsuro and Mizuki attended.
With Lisker dead, and even knowing what would befall him if his Control Medal were ever to be removed, Sho attempted to return to his normal life. His next day at school was rather placid, though not without some small annoyances along the way. Once they had finished the last of their work for the Sci-Fi Club, Sho and Tetsuro headed for their respective homes, clearly intending to walk together for as long as they could.
On their way home, Sho, curious about Agito since Mizuki had clearly taken an interest in him, began to question Tetsuro about the older boy.
Tetsuro, who had been close to the older boy some time ago, told him what he knew about Agito's past. Sho, who had grown up with a father, a mother, and a fairly normal life, was sympathetic to Agito's situation.
These moments of peace and reflection weren't to last, however; a small force of Zoanoids - numbering six in all, appeared just a few moments after Tetsuro had finished telling Sho about Agito's past. The two of them started running but Tetsuro, who lacked Sho's - by comparison - greater athleticism, soon began to fall behind. Pursued over the side of a steep embankment, Tetsuro and Sho were both seized by the Zoanoids who had driven them to ground.
Sho called the Guyver without hesitation, causing his captor to lose his grip and be knocked backward. After dispatching the four Chronos Troopers that had come after them, both Sho and Tetsuro watched in stunned horror as three of them were killed by a sudden barrage of acid spray. As it turned out, this was the calling-card of the newest Zoanoid - a Hyper named Zerebubuth - that Chronos had sent out in their latest effort to deal with him permanently.
At first, it seemed as if this latest effort of theirs was destined to succeed; Zerebubuth's armored carapace was impervious to Sho's punches, as well as resistant to his Head Beam. Zerebubuth was also equipped with bio-lasers on both arms, in addition to the three acid-dispensing tentacles on his head.
Sho was able to breach his carapace in the back with a powerful kick delivered with both legs. However, before he could capitalize on this newly-created weakness in Zerebubuth's armor, the Hyper Zoanoid spotted Mizuki, who had by extreme misfortune happened to be walking by. Leaping to the top of the embankment with a speed that belied his sheer size, Zerebubuth grabbed hold of her, intending to use her as a hostage.
However, while Sho himself was prevented from acting against the Hyper Zoanoid for fear of Mizuki's life, others were not so constrained. When Sho finally caught up, he found Mizuki safely on the ground, and a mysterious, darkly-armored figure crowned with six short spines standing over her. This, he soon came to realize, was the host of the third Guyver.
The next day started off rather normally, with a trip to school, and the work accomplished therein. Tetsuro thanked him for saving Mizuki from Zerebubuth, but Sho himself was of the opinion that it was his own involvement with her that had brought her into Chronos' sights in the first place. While this assessment was partially influenced by his own emotions, it would prove to be rather prescient.
When he received a note from Chronos, challenging him to meet them at Mt. Narisawa, the very place where he had first come into contact with the Guyver, and also where he had killed his first Zoanoid. There was a certain poetic circularity to their choice of battleground, but it would only become obvious after the battle had finished; no one in-universe would notice it. Sho was determined to go alone to the site, but Tetsuro wouldn't hear of it, and with some doing convinced him not to.
When the two of them arrived at the site Chronos had chosen, they were confronted by Genzo Makishima. Stripped of his position as one of Chronos Japan's managerial staff and - unknown to Sho and Tetsuro at the time - transformed into the prototype for the Guyver-killer Enzyme series, Genzo was quick to take the anger he felt at being so easily cast aside out on Sho. Transforming into the Zoanoid form he had been forcibly given, Genzo/Enzyme struck a devastating first blow: jamming his acid-secreting claws into Sho's chest, and this disabling the Mega-Smasher until the bio-armor could recover from the injury inflicted.
This, however, would take time; time was not on Sho's side in this battle.
With his Mega-Smasher damaged, Sho was left with only his melee weapons, something that would prove to be a severe hindrance when facing a creature like Enzyme; and also the later models that would come to bear that name. Hitting Enzyme's right shoulder with the Pressure Cannon, Sho was forced to dodge quickly as the Zoanoid whose later iterations would come to be known as the Guyver-killers swiped at him in retaliation. Enzyme's strength was great enough to both uproot and destroy the tree that he hit in place of Guyver I, causing it to snap like a twig.
Sho himself was the next to feel Enzyme's wrath; the Guyver-killer slashing him with claws and tail, leaving Sho with bleeding wounds on his arm, thigh, and head. However, while he had been fighting with Enzyme, the Guyver had been working to restore itself with a speed not seen in any other creature. Sho was surprised but pleased by this development, and would have obliterated Enzyme with his Mega-Smasher, if not for the fact that the Chronos agents dispatched by Richard Guyot to the site of their battle had managed to capture Tetsuro.
Sho, distracted by the thought of his friend in danger - a tendency that Chronos would use against him time and time again in the future - was quickly set upon by Enzyme. The prototype Guyver-killer was able to bite off one of his arms, and then to drive the large spike at the end of his tail through the young Guyver's mid-section. Weakened and in severe pain, Sho was unable to defend himself when Enzyme ripped out the Guyver's Control Medal, leaving him to be devoured alive by the armor.
The Guyver, however, was not a being to be killed so easily; even with its outer carapace dissolved and its flesh rapidly melting away, the Unit itself leaped forward to grapple with the Zoanoid that had killed its host. Grappling the oversized Zoanoid from behind, the remains of the Unit were nonetheless fully destroyed when Enzyme self-destructed on the orders of Richard Guyot. This was thought to be the end of things, and Chronos' agents were swift to take the Guyver's Control Medal - something like the computer-core of the Unit - back to the Japan branch's main office.
While it was held there, the Unit's Control Medal - having seemingly gone completely offline at that point, but in reality having merely entered a state of dormancy - reactivated and began to undertake the long, slow process of cellular reconstruction; this would result in not only the restoration of the Guyver's armored body, but of Sho himself inside it.
Guyver I reappeared before a group of Zoanoids, startling them enough that they immediately vacated the containment room where the Control Medal had been stored. The Guyver - with Sho still comatose inside the armor - burst through the steel door that had been closed in an ultimately futile attempt to contain the now rampant Guyver I. The four Zoanoids who attempted to bar the Unit's way after it broke out of containment were no match for the Guyver and were hence disposed of quickly.
The Unit's mindless, uncontrollable rampage through the halls and corridors of Chronos Japan's main branch continued, right up until the point that he encountered Tetsuro, still in the cell where he had been so unceremoniously shoved. The sound of his old friend's voice calling out to him woke Sho from the fugue-state that he had been in when the armor had regenerated his body.
Pulling Tetsuro free from the remains of the cell he'd been sitting in since his capture, Sho was at first shocked to see just how much damage that the Guyver had done without his consciousness to control it, and disoriented due to waking up in a place that was completely unfamiliar to him. This would not be the last time he would find himself in such a situation, however.
With full, conscious influence over the Unit's actions once more, Guyver I was no longer the ruthless, destructive berserker that he had been. He was not one bit less relentless in his pursuit of freedom for both himself and Tetsuro, however, as the Zoanoids attempting to block his path learned quickly. Blasting his way through the ceiling over both their heads, Sho and Tetsuro found themselves inside the main control center of Chronos' Japanese branch.
They also found themselves facing Richard Guyot.
Finding out that Guyver III had planted explosives inside the building - already damaged by both Guyvers in their respective rampages - Sho acted fast to protect the only person that mattered to him at that moment: Tetsuro. He tried to ask what side Guyver III was in fact on, but received only advice to use his Gravity Controller, and to hurry out of the building before it collapsed.
Volume 1 ended with Sho and Tetsuro hovering over the exploding Chronos Japan building, knowing that their lives would never be the same.
When the pair of them were able to return to school the next morning, stopping for a long moment to copy down their respective schedules for the day, they quickly found themselves confronted by an irate, worried Mizuki. Opting not to discus their absence for fear of drawing her too deeply into their battle against Chronos, Sho and Tetsuro split up.
However, Sho returned quickly to his friend's side after hearing him scream for help. Seeing what looked like another Zoanoid menacing his friend, Sho was quick to transform and confront it. However, that only led to the creature running from the room for its own incomprehensible reasons.
Find out from Tetsuro that that creature he was pursuing had first appeared as an identical copy of himself, sans clothes, Sho was shocked by the prospect. Asking Tetsuro about the fate of his Guyver's severed arm yielded only his friend's insistence that he'd been led away from the battleground once Sho had been killed - however temporarily - and so didn't know the fate of the limb in question. Making their way out into the halls of their school, deflecting a question from one of their fellow students, the pair of them continued to attempt to drive the strange creature to ground.
Tracking the creature through the halls, Sho found it facing Mizuki. Since she was at this point unaware of his circumstances, she naturally had no reason to assume that the clone - who had procured clothes for itself by some means at some prior point - was anyone but the real Sho. Once the creature had transformed, and Guyver I had jumped to her defense, Sho directed Tetsuro to protect her, and went after the creature.
Finding himself confronted by Guyver III, and then the creature - who transformed before his eyes into a clone of Sho himself - followed after the creature as it leaped away. Cornering the creature, Guyver III crippled it with a pair of shots to its legs with his Head Beam, and was about to finish the job with his Mega-Smasher when Guyver I intervened. Stepping aside, seemingly willing to let Guyver I deal with the ersatz Sho Fukamachi, Guyver III stood by.
In the 2005 TV series
As in the manga, Sho's first appearance was just as he departed from school, Tetsuro accompanying him on his way. At the lake, as before, he recovered the Guyver unit and activated it by sheer accident. Going on to fight the Zoanoid Gregole, the Unit killed the Zoanoid and left the demi-human to dissolve in the grass. Once he'd completed another day of school, with Tetsuro growing increasingly worried over their precarious circumstances, Sho was again forced into combat; this time with a small group of Ramotith led by a Vamore.
It was then that he and Tetsuro both realized how much danger they were going to be placing themselves in now that Chronos knew of them.
The next opponent that Sho had to face was a man named Kimura, who worked for Genzo Makishima, and who had been transformed into the Hyper Zoanoid Synevite. Once Synevite made the mistake of taking Tetsuro for a hostage, Sho - having initially been severely battered by the long tentacles of the Zoanoid, and lacking a method to inflict more than superficial damage on the soft body of the squidlike Zoanoid - found new resolve, and with it, a way to use the Guyver's Vibration Blades. Soon enough, Sho was forced to face the most dangerous opponent that he had come up against thus far: a Chronos-aligned Guyver named Oswald Lisker.
Forced to fight for his life against Lisker, not even minutes after he had been brutalized by the Hyper Zoanoid Synevite, Sho was only able to escape from the vicious Chronos inspector thanks to a fortunate malfunction from Lisker's Control Medal. Returning with Tetsuro to the latter's house, Sho rested from his battle. He also wondered about what he had just seen; while he and Tetsuro waited for Mizuki to finish preparing dinner, Sho discussed his misgivings with his long-time friend.
Then, hearing a yell from Mizuki, Sho raced up to her room to see if he could give aid during what he likely thought was some kind of a struggle. However, this turned out to be something of a miscalculation on his part, leading to a great deal of embarrassment on both his and Mizuki's parts. He did, however, stand just outside her door while she regained her composure.
The next day, with the two of them fully aware of the danger they were in - though not the full extent of it, admittedly - Sho and Tetsuro returned to school.
When the school day had nearly concluded, with the two of them protected from the hypnotic sound-waves that had been broadcast throughout the school to clear it out, Sho and Tetsuro left the room to find themselves standing alone in the deserted building. Not knowing what could have happened, the two of them swiftly found themselves confronted by a pair of Malcult. Sho transformed to deal with the Zoanoids, but then found himself forced to confront the Hyper Zoanoid that had been accompanying them.
Zerebubuth had arrived.
After battling the Hyper Zoanoid to a standstill, Sho managed to badly wound the armored Zoaform with a blast from his Guyver's Pressure Cannon. Recalled after taking damage, Zerebubuth dissolved the balcony that Tetsuro had been standing in, leaving when Sho acted to save his friend's life rather than engage in pursuit. The two of them hurried back to Tetsuro's house, both wanting to determine just how Mizuki had fared in the face of whatever had caused the mass exodus from the school building.
Both of them were relieved to find her safe and sound, though she was understandably confused about what had happened.
Sho in Warrior Guyver
Sho in Son of Mine ('verse)
As nothing in particular has been added or subtracted from his life or personality, Sho was pretty much the same as he appears in canon. However, he also feels the same guilt about Kenji Murakami being taken by Chronos as he does about his friend Murakami. He also forms something of a close relationship with Ryan Crouger, who returns the sentiment in his own way.
Sho remained in Japan while Ryan took the opportunity to search for the source of a signal from another Guyver that he, Agito, and Ryan himself had all sensed in America. He is often concerned for the younger Guyver's safety, but he knows that Ryan is as fully capable of taking care of himself as any other Guyver.
Still, that does not diminish Sho's desire to protect Ryan from the depredations of Chronos; it simply makes him more cautious about when and how he acts on that desire.
When Ryan returned to Japan, Sho woke up to greet him, though the boy himself wasn't particularly coherent when he did. Owing to the fact that he was nearly at the end of his endurance, both from the flight back, and the battle against four of the Zoalords that had taken place before it. Sho was concerned for his friend, but Ryan wouldn't hear it, insisting that he could take care of himself, and that Sho didn't need to worry about him.
The next time he appears in the series, he Agito and Ryan are fighting against Chronos' Zoanoid troops. After Ryan leaves for Los Angeles to give his aid to Sean and the ACTF, Sho takes refuge with Agito's Thunderbolts for a time, before moving into Shiyu Odagiri's mansion to stay.
When Ryan goes to ground with the ACTF, Sho remains to carry on the fight in Japan.