You are the last child in the Itoshi family, aka the younger sister of Itoshi Sae and Itoshi Rin.

Your two brothers used to get along very well, but now your two brothers are always fighting.. That makes you tired of course.

Therefore you create a time machine and go back to the past.

When you are in the past, the first thing you see is your two brothers looking at the sunset and the sea, and you remember that tomorrow is the day your older brother Sae goes to Spain.