With an impending typhoon, a boy and his best friend, K, go down to the beach in coastal Japan. They agreed to flee at the first sign of danger, but having been told by their parents that their area was currently in the eye of the storm, they believed there was very little imminent danger. That assumption is proved wrong when a loud gurgling noise begins; knowing immediately that it must be a wave, the boy runs to the safety of a nearby building. K doesn't notice as quickly as him, though, so by the time he is already to safety, K is still lingering on the beach. The wave appears, almost three stories in height, and it crashes on the shore, swallowing K in the process. The boy looks for K in the debris left in the wake of the wave, but there is nothing and no one on the shore. Searching, he sees yet another tidal wave approaching. When it is close, he notices something miraculous: K is happily gliding on the wave. Overwhelmed, the boy goes unconscious before seeing the rest of K's fate. Waking up three days later, the boy is sickly as he reckons with losing K and with the unbelievable sight that he's certain was real. Mourning K, he continues living his life. Decades pass, his father dies, and he returns to his hometown that K's death had driven him from. He continues to wonder about K's outcome—if he truly survived the wave, or if he had succumbed to it. He regrets not having saved K, since he knew the wave was building before K did. Instead, with his advanced knowledge, he ran away and saved himself. What K did was remarkable, the old man now believes, because rather than turning from the wave in fear, K embraced it and was thus able to ride it out.