Birthday: October 26

Yui Hongo is the Priestess of Seiryuu. An intelligent and mature girl, she is a tenth grade student and Miaka Yūki's best friend. A passionate person at heart, she tends to see the world in black and white terms and is easily infuriated with perceived betrayal. Yui is confident and bold with everything she does, but longs for someone to take care of her. It is revealed in the manga that Yui cut her hair to avoid all the attention she was getting from boys.

Yui is initially transported to "The Universe of Four Gods" with Miaka, but almost immediately returns to the real world and becomes the one who reads the book in order for events in the world to progress. However, she becomes trapped in the book while trying to help Miaka return to the real world. Afterwards, bandits capture Yui and knock her unconscious. When she regains consciousness, she believes she has been raped and, distraught, attempts to kill herself. Nakago rescues her and convinces her that Miaka is responsible for Yui's misfortunes, leaving Yui unaware that Nakago had saved her before the incident involving the bandits and that she had not been raped at all. He manipulates Yui into becoming the Priestess of Seiryū, convincing her that it will allow Yui to take revenge on Miaka. She eagerly agrees, swearing to fight Miaka and to take away her lover, Tamahome, whom Yui has become attracted to.