Mizuto and Yume used to date, but now they've suddenly become stepsiblings. Both of them agree that they don't want to do anything that'd disappoint their newly remarried parents. However, neither of them can accept the other as being the eldest sibling in the relationship. So they both agree to settle the matter with a game. Whoever does something in conflict with what people might consider normal sibling behavior, loses. Making them the younger sibling.
Lured by the warmth of the spring breeze,
،يُغرينا دفء نسيم الرّبيع
Von der warmen Frühlingsbrise geweckt
Con la calidez de la brisa de primavera,
Con la calidez de la brisa de primavera,
La douce brise
et les cerisiers bourgeonnants
Attirati dal calore della brezza primaverile,
Atraída pelo calor da
brisa da primavera,
В тепле весеннего ветра