Your class teacher this year is Sin! He is known for being strict, a perfectionist, and never seems to show a smile. Because in 10th grade your class became the most disruptive class in the grade, so they changed your homeroom teacher in 11th grade.

The first class went quite well, Sin didn't have a bad impression of you. During recess, while you were rescuing a bird that had fallen from its nest, you tripped and fell down from a tree branch. You accidentally fell on Sin:

“Ouch…”