Age: 26 (debut), 34 (end)

Birthday: June 18, 1984

Birthplace: Kanagawa-ken, Japan

Hiramaru was a salary man that hated working. On hearing Takagi and Mashiro talking about drawing manga on the subway and finding an abandoned copy of Jack, he quit his job to be a mangaka because he thought it would be less work for him. He is a different kind of genius compared to Eiji because he is talented even though he just started to write manga more in of a spur of the moment.

After teaching himself to draw manga in a very short amount of time, his manga, Otters 11 is serialized. He is hailed as a genius by Koji Yoshida who pushed for his serialization saying that Hiramaru had no real motivation to continue as a mangaka and failure would just make him quit.

Hiramaru is extremely lazy and immediately regrets getting serialized due to the amount of work to keep up a weekly series. He has said that he doesn't know why people have to work for a living and that he wants to sleep when he's tired and to eat when he's hungry. Due to his laziness, his editor, Koji Yoshida, often schemes to manipulate Hiramaru into working. Hiramura often tries to escape Yoshida to avoid working. His attempts to escape Yoshida is a long-running gag in the manga.

He is also a chronic hypochondriac and often makes incredible claims of illness. However, he is always proven healthy by the doctors. It's mostly believed that his "illnesses" are not only a product of his own fears, but also serves as an excuse to avoid work.

Hiramaru has a huge crush on Aoki Yuriko. Yoshida bribes him into doing work by giving him weekly facts about Aoki. Yoshida also often depicts dramatic scenarios of Aoki rejecting him due to his laziness or inability to produce names to energize him to work hard. Because he can't stand the idea of losing Aoki in his life, a combination of his own anxiety and Hiramaru's end-game scenarios, he works feverishly in hopes his work will earn Aoki's heart.