For God’s sake, she’s a tsundere moe-character! What did he expect? That she behaves like a reasonable person?!
C3 has a hard time selling itself as it seems just like the standard-treatment you have seen countless times before. Guy living alone is suddenly forced to live with a girl and he has a childhood-friend. The story is about flashbacks and the main lesson of life that as long as you see the world as a fluffy place of happiness it IS a fluffy place of happiness.