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 arrives at a village where the men are in a heated discussion about the mountain. After learning of Ginko's identity they ask for his help to find another Mushi-shi called Mujika, who happens to be the master of the mountain. While on his trek through the mountain Ginko stumbles across a boy who's also looking for Mujika. Later they manage to find Mujika but this isn't the end of it.

It is spring, and Ginko is taking a boat through a river, when the boat's boy, Kaji, asks Ginko whether he could help his mother, who's forgetting things and can't sleep. At first glance it may appear to be progressive amnesia, however something isn't right.

Ginko arrives at a secluded place, to meet an old acquaintance, who seems to be in charge of a large volume of archival, confidential text. Ginko is allowed to read it, and discovers it is the work of Tan'yu, a writer. Tan'yu is the descendant of the Karibusa family, being born with a black mark on a part of their body.

In a cold mountainous region, Ginko is wandering around the snow cover plain when he hears a sound ringing through the cold air and he also notices some rust on a tree. Ginko enters a nearby town to find the rust covering everywhere, including the people. The village chief tells Ginko that this is a sickness that has been affecting the town for 14 years that the people have been slowly losing the movements of the limbs and it's said that a girl called Shige is the cause of it.

A restless man, Kanta, on his way home to his wife and young daughter (Futaba), sits down to rest in a forest. He is tired and thirsty so he eats a red fruit that was lying on the ground near him, and gives thanks to the plum. Some time after this, he starts having vivid memories both in his dreams and while awake of times going back before his birth. He goes looking for a huge tree but finding it does not make him happy.