Brash, self-centered, and noisily infatuated with Matsuya and Ropponmatsu Unit 1, Iwata is generally disliked but tolerated by his neighbors and co-workers. His tendency to make inappropriate statements towards women and his rivalry with Ropponmatsu Unit 2 often lead to him being physically assaulted.

In volume eight of the manga, Iwata suddenly dies of colon cancer, but is promptly resurrected, with his brain given an android replica body by Shioji. There are many theories about his relationship with Watanabe due to the strange attachment he has toward his fellow roommate. Watanabe on the other hand, hates Iwata's guts.