Yuzan is having a birthday party and it is imperative that Haru attend. It's not so much that Yuzan wants Haru to be there as it is a demand from their father. The Yoshida family requires certain appearances to be kept and Haru being at the party will show that the family is together and not the actual mess that it is. But attending the party comes with great challenges. Haru may combust when he feels that attempts are being made to control him.