Ginko hears a rumor around town that a man is has prophetic dreams every once in a while. He suspects that Mushi are living in his dreams. He gives the man medicine to keep them under control and says he will come back when he has used about all of them. When Ginko returns, the village is deserted and torn up. Ginko finds the man alone in is house. The man then tells him about what happened while he was away.

On a rainy day Ginko takes a rest from his travels and comes across a man named Kourou who seems to be obsessed with a rainbow. To pass the time Kourou reminisces in his past, with the events which led to him pursuing rainbows whenever they appear. Ginko explains to him that the rainbow which he is searching for is actually a Mushi known as "Koda" but there seems to be more to it.

Ginko is waiting along the sea shore, for a transport to get him across the bay when he meets a man called Shirou, who lost his wife under strange circumstances. Ginko seems interested and decides to listen to his story about how he lost his wife in a swarm of sea snakes, during fog. Ginko later comes back with information on the Mushi that caused the bizarre events.