After learning about the legend of the Eternal Tree, Nodoka, Chiyu and Hinata find the tree in order to make a vow of friendship under it. However they are shocked to discover that the tree was killed during a recent storm. They also meet an old man who tells them that there is no such thing as eternal friendship. The girls learn from the tree's spirit that the man's name is Tetsuya, and that he made the vow with his two friends Fumi and Hideo 50 years ago. The tree spirit asks the girls to find Tetsuya's friends and bring them together before the tree is cut down. Nodoka agrees and the girls manage to find Fumi and Hideo, only to discover the truth behind their separation. Unable to convince the three to come together, Nodoka, Chiyu and Hinata make the vow under the tree, before deciding to hold a farewell festival for the tree. On the day of the festival, Batetemoda creates a MegaByogen from the tree spirit, causing Tetsuya to try and defend it before being rescued by Fumi and Hideo. The girls transform and defeat the MegaByogen, afterwards Fumi, Hideo and Tetsuya renew their friendship before Fumi reveals that a new sprout has grown from the tree.