Narumi Kanai is amicable and benign. He is also a teacher at hanabi's school, who he cares deeply about but never views her relationship wise, more like a precious little sister.

Spoiler

Narumi appeared to fall in love with Akane, although he knew that she had a hobby of sleeping with other men. He is prepared to cherish her for the rest of his life even if she cheats on him, he just cares about her happiness.