Kuro-chan and Shiro-chan

Kuro wants to become friends with Shirai, because she admires her and feels they have something in common (i.e. hating Aoki). As a sign of friendship Kuro gives a white hair pin to Shirai and wears a black version herself. One day, Shirai inadvertently hurts Kuro's feelings by dismissing her infatuation for Rin as abnormal. After realizing what she has done, Shirai eventually decides to wear the white hair pin in front of Kuro, making her very happy. Shirai ponders what her life would be like if she had a friend like Kuro in her youth.