Yamada woke up on a deserted island without any memory of how he got there. He refused to give up hope, despite the lack of passing ships, and found his sports bag, suggesting he was on a school trip. However, he had limited supplies of food, so he decided to build a boat to escape within seven days. Initially thinking he was alone, he eventually discovered Imaise Chika clandestinely dining on his food. Together, they collaborated on building the boat.
Although the vessel was only large enough for one person, Yamada left to seek help. However, he returned after discovering that Imaise had kindly shared her portion of the rations, which remained mostly untouched. He also recognized her ingenuity in creating an oar from a fishing spear. He concluded that they could survive together on the island for an extended period, so they continued living together.
