No. 502 is a robot that possessed Professor Hayase's body.
Hayase (No. 502) wanted to provide Fuyou, his daughter, with more friends. He also experimented with fusing Fuyou's body into Tama (who was No. 0 at the time), but this tragically resulted in Fuyou's death. Despite not having a soul implanted in him, No. 502 collaborated with another individual who was eager to take over the Fuyou Project, along with a pink-haired robot maid.
When Tama showed Gintoki and Kagura Professor Hayase's body, Hayase began to creep up towards Tama’s head, attempting to fuse his own body with No. 502’s. After retrieving Tama’s head, No. 502 noticed that the seed was missing. To recover the seed, he planned a hijack at the Terminal. The plan nearly succeeded, and he was about to use Shinpachi as a test subject when Gintoki tried to destroy No. 502.
It was later revealed that Professor Hayase had been working alone all along. Even after Fuyou and Gintoki explained this to him, No. 502 continued with the hijack and attempted to kill both Shinpachi and Gintoki. However, Kagura and Gengai’s robots intervened, preventing No. 502 from killing Gintoki. Tama also prevented No. 502 from escaping. Eventually, Gintoki managed to move No. 502 and Hayase’s soul into the power of the Terminal, ultimately leading to their demise.
