The episode opens with the girls looking for Bokusen-Oh so they may find the Kyuyokon root, which is essential to make Towa's new sword.
By the Tree of Ages, Sesshomaru watches over Rin as Jaken informs him where the girls have gone.
Begin flashback to 14 years ago, just after the girls were born. Rin was about 18 at that time. She was watching Sesshomaru and InuYasha take care of the Grim Comet when Zero approaches her. Zero inflicts Rin with the silver-scale curse. Soon she will be covered in ugly silver scales and slowly rot away alive. Sesshomaru arrives but cant do a thing to Zero as she has attached herself to Rin with the thread of fate. If they tell her where the half-demon twins are, Zero will lift the curse. Rin forbids it for she would rather lose her life than the life of her children.
To slow the curse, they seal her in the Tree of Ages. Jaken fears InuYasha and Kagome will go after Kirinmaru and Zero. If they kill Zero, then Rin will die too. (This is why Sesshomaru agreed to accompany Kirinmaru when he wanted to slay InuYasha.)
After the forest fire, Jaken saw that the scales were spreading. The Spirit of the Tree of Ages says, "To stop the curse, you must freeze this woman's time permanently. Use the butterfly to bring dreams to her. Take the Butterfly chrysalis and attach it to someone who is close to the woman and grow the Dream Butterfly. If you use the Butterfly to keep giving her sleep and dreams, this woman will continue to sleep and dream. That will stop her time and also slow the curse down." Setsuna is whom he attached it to. End Flashback.
Returning to the girls, Setsuna has stayed back with the excuse that she left her violin somewhere, but in fact, she sensed they were being followed. Three demons, one with the green rainbow pearl in his eye, attack her. Riku defeats them and grabs the rainbow pearl. Setsuna is very skeptical of Riku's intentions, but allows him to be a bodyguard for Towa's sake. Before he leaves, Riku gives Setsuna directions to Bokusen-Oh.
Using Riku's directions, the girls stumble upon Bokusen-Oh, who happens to be a 2000-year-old tree. Moroha sweet talks him into giving them the information they need to find the Kyuyokon root, however, they must get through a barrier on Mount Musubi.
At Zero's dwelling, Riku brings her the remaining rainbow pearls. Now she can restore her demon powers. She looks into Riku's eyes and talks to Kirinmaru. Riku is confused, but as it turns out, Riku was originally a horn cut off from Kirinmaru during a battle with the Great Dog Demon. As a part of Kirinmaru's body, everything Riku hears and sees goes directly to him. Zero tells Riku not to show his face around her again unless he wants her to kill him.
Zero learns that the memories of those who had the rainbow pearls previously are grafted as an extra layer in the pearl. She is furious...especially with Sesshomaru!