It's been so long I got no clue what's going on
Umm i think this is taking place just a few days after the ibrary" or small storage building was set on fire by an unknown person and shiki and kouran were trapped inside of the small building but shiki "sacrificed" himself to help kouran escape the fire and shiki gets a burn on his hand. So kouran decides to help shiki with his job an stuff out of partial guilt? Or maybe jus becuz she wants to help and loves him. Oh rite and the reason why shiki and kouran was in the little storage area in the first place is bcuz kouran was avoiding him after he rejected her love confession so he got fed up and kind of cornered her in the storage area
I have a strong feeling that his brother did it