Fumio Fukamachi is the father of Sho Fukamachi in the Guyver anime. Little is known about him other than that he is a widower and he has had to raise Sho alone since Sho was only 3. He is oblivious about his son's struggles as the Guyver until he is abducted by the Chronos Corporation and held hostage at their Mount Minakami base. While in captivity, Fumio is subjected to Zoanoid processing by Dr. Barcas and is transformed into the new Guyver-Killer creature, Enzyme II. After optimization, Fumio is sent back to his cell and remains there until being rescued by Sho. Sho takes him away from Mount Minakami, only for Fumio to transform and attack him. Manipulated by Barcas's telepathy, Fumio inflicts mortal damage on the Guyver - who cannot fight back without killing his father - and rips out part of his brain. Rather than what Dr. Barcas had planned, the bio-boosted armour shifts into a self-defense mode and mercilessly attacks Enzyme II. He severs one of the creature's clawed tentacles and an arm, then obliterates him with the Mega-Smasher. Fumio briefly regained consciousness during the battle and was aware when the Guyver fired on him; he screamed Sho's name as the Mega-Smasher beam engulfed him.

After Sho regenerated from his wounds and saw what he had done to his father, the trauma caused him to repress his memories of the event and subsequently become unable to bio-boost. Sho would remember the truth and regain the power of the Guyver after an encounter with the vengeful Aptom, eventually coming to terms with the loss of his father and finding the strength to continue the battle against Chronos.

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