Kazu

Kazu is one of Satoru's primary school classmates and friend.

History
Although he did not play a role in saving Kayo, he did play a part in saving Aya.

They first met when Satoru, Kenya and Hiromi were trying to impress Aya. During that time, Aya insulted their hideout by calling it childish. Kazu, then came out of his hiding place and defended it by calling it a "man's dream".

After that, Aya seemed to have been attracted to his "manliness" and spent a lot of time with him and his friends.