|Manga Debut||Chapter 33|
|Anime Debut||Episode 67|
During the Parent's Participation Day at Namimori Middle School, Reborn takes over the class after the teacher leaves to take an unconscious Gokudera to the nurse. When Reborn tells the class to solve a complicated equation, Osamu stands up, saying that he refused to put up with him. Reborn promptly attacks Osamu and his mother with two pieces of chalk, knocking them unconscious.