Tsumi to Batsu no Spica

Tsumi to Batsu no Spica summary:

Hatori, a high school teacher leading an ordinary life, notices one day that his student, Spica Tsumugi, is being bullied. On a rainy day after school, Hatori finds himself alone with Tsumugi by chance.
Hatori tells her, "I'll do something about it!" but Tsumugi gently takes his hand and says with a smile, "Hatori-sensei, you're such a liar."
Teacher and student… two people who should not get too close. This somewhat bewitching girl will dramatically change Hatori's ordinary life.