Atsuhiro Kagari is a main character of the series Akkun to Kanojo. Although at first glance it seems that he doesn't care about Non, His girlfriend, being apparently mean and harsh towards her, this is actually only a mask to conceal his true feelings. On some occasions, he shows his caring "dere" side to her, and calls her by nickname Nontan as a sign of affection and closeness with her.
Chihiro Kagari is his younger sister, and Masago Matsuo is his classmate and close friend.

(Source: Akkun to Kanojo Wiki)