Hyakka is the eighth son of the Otori family, a prominent clan of fire users with a history dating back over nine centuries. With the death of his immediate elder brother, Hyakka was tasked with replacing him as a member of the Goko Clan. Hyakka is from the Heian Period like Mao and because he proceeded Mao in joining the Goko Clan by ten days Mao refers to him as "Lord Hyakka". Cocky and abrasive, Hyakka is rarely afraid of giving his opinion on matters. Because of his fire abilities he is ill-matched against water users like Mokuzu and Shiranui who are able to cancel out his attacks. Hyakka is also one of Mao's fellow pupils that was invited into the Five-Sided Room where he was tasked with assassinating Mao. Because of the screens that obscured the other sides of the room, Hyakka had no idea who the others assassins were, though an inquisitive outburst from him revealed his identity to the others who were summoned.
Muddling through his long life, Hyakka has worked as a carnival performer and now a ramen cook and, like Mao, also gained immortality and has lived a mostly anonymous existance until the 1920s when his past begins to haunt him. He is initially mistrustful of Mao, believing that he was responsible for the death of Sana and that he intentionally usurped Byoki's wicked powers. Eventually he is convinced that Mao was framed for Sana's death and that his even-keeled old friend had been set up in an elaborate conspiracy centuries ago.
In the early 1900s Hyakka encountered another face from his past- Hakubi, the metal user. Hakubi was particularly ill-suited to face off against Hyakka due to fire easily vanquishing metal, but the two were able to battle to a draw. Hyakka severely wounded the soldier while Hakubi was able to cut out Hyakka's eye. Unknown to Hyakka was that Hakubi had a long-simmering resentment for the small fire-wielder as he believed he was undeserving of his place in the Goko Clan, which Hakubi thought was only given to Hyakka due to familial connections.
The Meaning Behind the Name - 百火
Hyakka is written with the kanji for "one-hundred fires" (百火), which is particularly suitable considering his gifted flame-wielding.