3 Idiots

Three bullies from Osamu and Yūma's school, who are collectively known as 3 Idiots. In the manga, their names are not given and are referred to as No.1, No.2, and No.3. In the anime, the credits gave them the surnames: Eida, Bitō, and Shiihara.

Trivia

 * No. 1 is "Ringleader" of the group. He is the worst of all the delinquents but Ashihara wishes to improve his danger detection skills so he could survive.
 * No. 2 is "The Annoying One", The author doesn't exactly hate him however he finds him easy to draw.
 * No. 3 is "Roots Showing". According to Volume 1, his delinquency is his hobby. He has good grades, and his family is quite rich.