In the novel and manga, Boy #17 Mitsuru Numai serves as Kiriyama's devoted second-in-command within the street gang.
He was a stern classmate. After Kiriyama instructs the gang to gather at a specific location on the island, Mitsuru stumbles upon the corpses of his fellow gang members, along with Izumi, an innocent bystander. Shortly after this discovery, Mitsuru is killed.
(Source: Wikipedia)










