A young high school student named Makoto Suzuki moves to Tokyo from Nagoya with his mother, who plans to start a new company. Makoto knows very little about Tokyo, so after dropping his mother off at a hotel, he decides to go exploring. On his way back from buying a snack at a convenience store, he almost gets run over by a speedboat on a flooded street. He is saved by the store's little sister, Shion, who sees Makoto drowning. He gets home safely, but is stunned to see that his neighbourhood is not the way he left it.