Following 4th Subdivision leader Xia-Long Miao's defeat at the hands of Fang Fang Huang and Yukari Sendo, Fang Fang attempts to convince Xia-Long to become their friends and desert Fairy Tale. Just then, Gairen Yuki appears and reminds Xia-Long not to follow in the steps of his father (who was brutally punished for disobeying orders). Xia-Long breaks into a rage, asking Gairen how he knows about the incident regarding Xia-Long's father. Gairen does not reply; instead, he melts all the pillars in the room and ominously tells Xia-Long that all "those who betray him await a gruesome death". The entire ceiling collapses upon Xia-Long, Fang Fang, Yukari and Routier.
Moments later he reappears to kill Moka Akashiya but is haulted by Fang Fang and Yukari who have unfinished business with him and become his opponents. When Fang Fang slashed Gairen, he realized that he didn't feel anything when he hit him and that Gairen's plated armor is empty.
- Though Gairen appears to be just another Subdivision leader serving Gyokuro Shuzen, he is in fact a direct disciple of Masked King, founder and leader of Fairy Tale. He appears to know a lot about events only known to Xia-Long and the Masked King, such as the Masked King brutally stuffing Xia-Long's father into a briefcase for signing a truce with the Huang Family without his consent, and the Masked King's subsequent warning to Xia-Long.
- It could be that Gairen was created by the Masked King's power seen as it left Gairen's armor by his defeat.
- Gairen can best be described as a haunted ghost wearing a plated suit of armor.