Tenshi Dattara Yokatta

All Kako wants is to have the important people to her smiling. She treasures her two childhood friends so much, which is why she won't confess to Taisei about her feelings for him. One day, after Taisei's recovery from an accident, he then tells Kahoko that he and Uina have how started dating. She believes that their relationship is "unbreakable," or so she thought it was.

(Source: Lovesick Alley)