Suboshi, also known as Shunkaku Bu, is a Seiryū Celestial Warrior and the younger twin of Amiboshi. Born under the star Horn, he possesses the Ryūseisui, a double meteor bell that he can control with his mind. Suboshi and Amiboshi share a unique ability to communicate by writing messages on their bodies.
Suboshi's personality is marked by impulsiveness and stubbornness. He becomes fiercely determined once he sets his mind on something, often disregarding reason. The brothers' closeness stems from losing their parents early and enduring a difficult childhood. Suboshi's devotion to Amiboshi is so strong that he is willing to kill to protect him, even eliminating fellow Seiryū warrior Tomo without hesitation.
Suboshi falls in love with Yui Hongo, who shows him kindness after Amiboshi's apparent death. This leads him to develop intense hatred towards Miaka for supposedly abandoning Yui and jealousy towards Tamahome, whom Yui loves. Believing Tamahome responsible for Amiboshi's death, Suboshi murders Tamahome's family in revenge.
Despite being reunited with Amiboshi, Suboshi chooses to save his brother by administering a potion of forgetfulness when Amiboshi is near death. With his memories erased, Amiboshi is saved from sharing the fate of the other Seiryū warriors. Later, Suboshi uses Yui's school uniform ribbon to cross into the real world, attempting to kill Miaka and Tamahome but ends up killed by his own weapon, vanishing soon after. The ribbon remains in the real world, and Miaka returns it to Yui.
