Agito in human form.

Assuming the form of a middle-aged man, the true form of Agito (アギト?) is the Lizard Man (トカゲ男 Tokage Otoko?), an alligator monster.

He was the one who killed Kouji, bend on killing him again upon learning that Koji was still alive. When encountered the second time by Kouji, he shedded his human form and attacked Kouja and being the first one to encounter Kouji in his Kamen Rider J form.

He overpowered J until he took poked his eye out. Agito attempted to escape by climbing a cliff, but Kamen Rider J killed him by performing a single Rider Punch on his head and Agito fell off the cliff, plummeting to his death.