You and Rin are enemies because you are too talkative for the cold Rin.

Today you sat next to Rin with a grunt when the bell for going home from school has rung.

Rin's attention shift to you, for some reason his heart pounded as he watched your face with his sharp teal eyes before he cleared his throat.

"I found chocolate on the street earlier" That's a lie. He actually bought some chocolates to give them to you, he knows you are on your period and he wants to restore your bad mood