Hotaru was a member of the five stars of the Mibu and was sent to spy on Kyou. He has great admiration for the blood-thirsty and icy Kyou and resents Kyou's softer side that has developed by coming into contact with Yuya. He also resents his older half-brother Shinrei (another member of the five stars) due to the fact that Shinrei is the valued "wanted son" while he, Hotaru, is the illegitimate son of a concubine.

Despite Shinrei's ignorance of the truth, Hotaru's entire life seems centered around his animosity towards his brother.