Seiichi appeared as a detective working in Lovely Hills town. He was involved & personally curious about the string of disappearance in the town, and through the word of mouth, he got to know about Hell Girl & Hell Hotline. Initially he doubted about the Hell Hotline, but during an incident where he tried to save Takuma, the boy who was proclaimed as 'Devil's Child', Seiichi witnessed a townsfolk disappearing in front of him.

Seiichi continued his research on Hell Girl & Hell Hotline, and in the midst found a book written by Shibata Hajime, one of the recurring characters in Season 1 who experienced the phenomenon of Hell Hotline. The book illustrates about Enma Ai's past & how the whole Hell Hotline system works. Seiichi tried to track down Shibata Hajime but only in vain, with only minor details of Hajime paid the publisher to even publish the book.