12-year-old Sakaki Jirô is introduced to the viewer at the breakfast table with his parents. He is getting ready to go, with his friend Yurika, to take a tour of his uncle Dr. Sakaki's (a.k.a. Dr. Lee) cryogenics research institute lab. While there he gets accidentally trapped in one of the cryogenic chambers during an earthquake and revives in another time where apes rule and there are no humans, other than Gôdo. Because their similar age, he hit it off Pepe.
Jirô proves quite skillful at escaping from ape custody and evading capture by Gebâ's soldiers. Ultimately the three humans find a way of returning to their own time, where Jirô is reunited with his relieved parents.
In the heavily-edited and English-dubbed version, "Time of the Apes", he was renamed "Johnny".