Onizuka Chris - The Invisible Man and His Friend's Mom - Hentai Manga

Hiroki and Fumihiko have been friends for the longest time, and Hiroki once saw his friend’s mom as a mother figure that was missing from his own family. Those feelings eventually evolved to something more powerful. He can’t just come out and admit how he thinks of her, but perhaps the invisibility serum he obtained from his university research lab will help him find a different solution.