Four high school girls lie sprawled on a sandy beach. After an accident strikes their class trip, the girls find themselves stranded on a deserted island. While the four introduce themselves, one of them, Onishima Homare, seems unusually calm. Then she says something shocking! "This isn’t the first time I’ve been stranded."

In order to procure water, the girls explore the island. Homare and Asuka find a dry stream bed. In order to get water from the dirt they dig up there they’ll have to…!? Meanwhile, left behind on the beach, Shion and Mutsu, both faint from dehydration, make a certain promise…

Homare and Asuka enter the forest to find food. Asuka is overjoyed to find a plant that looks like taro, but Homare points out it could be dangerous. When Asuka throws a tantrum saying she wants to eat it, Homare gets fed up, suggests they check to see if it’s even edible or not, and suddenly flips Asuka’s skirt up!?

One day, Homare and the others find evidence of squirrels and rabbits, and quickly decide to lay traps for them. In order to survive, they use what they can find on the island, and after some hard work, they have a real trap! Lightheartedly, Asuka decides to try the trap out, but…

Homare and Asuka go diving for food. When underwater, human vision blurs, however using a certain technique creates improvised underwater glasses which they use to look for turban shells and oysters, but… The severe conditions begin to take their toll on the girls both mentally and physically. Homare remembers something her father taught her — "When things are tough, when you’re sad, have a barbecue."

Asuka and Mutsu go to check the trap they set. Just as they’d hoped, there’s a rabbit caught in the trap, but there’s no time to call in the reliable Homare! If they leave it, it might get away…! What will they choose to do for the sake of survival?!

To prepare for the possibility of their cast-away life lasting longer than they thought, Homare and the others decide to explore the island, and they spot, of all things, a house! With hopes of rescue rising in their hearts, they race forward, but what they discover is the ruins of an abandoned building… Noting the despair of the other girls, Homare finds an item they’ll need to survive the island!