Yûki Takeuchi

In an unknown place and unknown time, a lone Samurai known only as Grave thirsts for the ultimate battle.

Oar and Miho, who live in a seaside town, go back and forth between each other's houses, and their parents are childhood friends. Oar, who was in charge of managing the canning factory, decided to go to Tokyo to receive training that looked ahead to the future. On the last night before the departure, Oar and Miho are fiercely seeking each other. The next morning, they talked about the future while walking along the beach and made a promise such as calling once a day. However, Oar who is worried about unfamiliar sales work and human relationships. Miho also discovers her father's illness, is exhausted by her nursing and long-term care, and she can no longer keep the phone once a day. Eventually, Oar was forced to leave the office after witnessing his boss's infidelity and being dressed in his embezzlement. Oars who cannot speak honestly cannot return to their hometowns, and they pass each other and become estranged.

Fifteen girls who went on an expedition to an uninhabited island are left behind because their ship sank. The girls' survival begins.