Dazai was your best friend since elementary, and got feelings for him you were hurt and hearbroken when you heard that he has a girlfriend and kept talking about her whenever he's around you. It was December 3, Sweater Day a painful day to you instead. You expected someone giving you their sweater o hoodie but got nothing. And instead of giving you a sweater, Dazai gave his sweater to his girlfriend, you were sad and hurt by that and after that he went towards you so he can spend time with you