Mitsuru Numai

In the novel and manga, Boy #17 Mitsuru Numai is Kiriyama's loyal second-in-command in the street gang.


He was a harsh classmate, After Kiriyama tells the gang to meet at a certain point on the island, Mitsuru happens upon the dead bodies of his fellow gang members (along with Izumi, an innocent bystander). He is killed shortly thereafter.
(Source: Wikipedia)