Those days were like a cradle: peaceful, yet transient.

Battler leads the sort of peaceful, everyday school life, together with the exchange student Beatrice, his friend Amakusa, and his junior Ange. Every lively day spent with them flows happily. But like a dream, this time won’t last forever. In those peaceful days, a fatal mistake was made.

Something was forgotten, yet it can’t be recalled…

These days begin to repeat, all the while an answer is being searched for…