Last Waltz: Hakudaku Mamire no Natsu Gasshuku

It was just supposed to be a summer training.... Yuki is a caretaker of the baseball club. She and other members stay at a training camp on the isolated island now. But one day, a civil war breaks out. Male teachers leave the island to see what's going on. However, they never come back. Several days later, they know that their ship is wrecked....