Kazuki Hoshino

 (星野 香月, Hoshino Kadzuki ) is Ichika Hoshino's younger brother. He is a high school student attending Kotomine Private School. He lives in the same house as his sister but is rebellious and they are not close. However, he is sociable outside and is popular at school. He is a band member and has pretty good guitar skills.

History
Kazuki is said to have been the pride of the family, being able to master many talents and such with ease compared to his older sister, who was average. When he went to high school, he insisted on attending one in Shinjuku. His parents allowed him on the condition that he live with Ichika, who left Niigata to become a police officer. Ichika mentions that they used to talk while living back in Niigata. However, after Kazuki moved in with her, their relationship soured.

Personality
Kazuki is recalcitrant and brusque with Ichika, preferring to keep her out of the loop in all his affairs. This side of him is very antisocial. He shows a different side to his own circle, like Aki to, who is his best friend.