Toshiaki Hayami, also known as Bio-Freezer(バイオ·フリーザー/速水利章 Hayami Toshiaki/Baio Furīzā) is one of Dr. Odagiri's assistants and is the sole survivor of the group of scientists that escaped in the Relic. The scientists were infected by a deadly virus as Chronos' means of keeping them under control. The only way to escape death is to be supplied with regular shots or to become Zoanoids. The only way to become a Zoanoid and yet not be slaves to the Zoalords is to become a Lost Number. Since supplies of the medicine were running out, they resorted to attempt to becoming Lost Numbers. Hayami was the only scientist that survived the process, becoming "Bio-Freezer". He possesses the power to affect the temperature of the environment around him to a certain extent. Aptom finds him and, once he realizes what Hayami is, brings him to meet the Guyvers and their friends. Unfortunately, later on his mission with Sho to save Aptom, he sacrifices himself to save the latter.
He is a member of the scientist group who were secretly working to oppose Chronos.
He had been inducted against his will into the organization, bound to it by an insidious virus which increases mental acumen, but kills the host without regular injections with an antidote. While working for Chronos at Relic's Point, their base under Mount Minakami, he came into contact with Dr. Odagiri, another captive scientist. He, and at least three others (Torii, Fujiwara and Ijuin), conspired to undermine Chronos in any way they could, and they got their opportunity when Guyver III was leading his friends through some of the outlying tunnels of the complex. The scientists helped the Guyvers and their friends hide out right under the nose of Chronos.
When Relic's Point was destroyed, Toshiaki escaped along with his friends, but they decided to split off from the others to pursue a cure for the virus that was still inside them. The only choice they saw, considering the knowledge and resources they possessed, was to undergo Zoanoid processing... but skew the process, so that they would be processed into Lost Numbers, free from Zoalord control. Accepting the danger, they entered into the process, knowing it was the only way to survive and be free.
Toshiaki Hayami was the only survivor.
Seeking out the Guyver's companions, he was intercepted by another Lost Number: Aptom. Soon, all allies were united, and Hayami proved a loyal friend and a deadly foil for some of Chronos' most dangerous warriors. His battleform possessed the unique ability to freeze his opponents solid by expelling super-cooled helium, and was codenamed "Bio-Freezer" in his Chronos file for this reason.
When Aptom was taken captive by Chronos, Hayami joined Guyver I on the mission to retrieve him. The mission, however, turned out to be a trap with Aptom both the bait and the spring. While under control of Zoalord Kabral, Aptom stabbed Hayami in the chest with a High Frequency Lance. In his final act Hayami froze the lance as it pierced his chest. The tip of the now brittle weapon broke off inside the Lost Number's body. As it thawed the fragment of Aptom from the lance began to absorb Hayami's body. As Aptom regained consciousness, he felt as if he inherited Hayami's spirit and swore to fight in his name.
Indeed, later that night Aptom used Hayami's freezing power, which he had absorbed into himself, to destroy Kabral forever.