It's a Haimushi (yokai) that tried to infect him, and instead became bound to his body since he's immortal and not quite alive, and spent ages feeding on the jade that he eats. Turned into a lunar moth familiar, but evolves or devolves, based on the canon context into other specific forms.
If curious:
Berserker Asahi. Winter coat.
He's a fire Komainu~
Jade claws and fangs.
Eyes slitted in draconian rage.
Axe head melting at his touch.
Chainmail coif simmered down to a scarf.
Familiar purveying the carnage as a centipede.
And why defend with a shield when you can bash with it?
Comments
Judging from the heating on the metal and singing on the clothes it's hot fire.
Berserker Asahi. Winter coat.
He's a fire Komainu~
Jade claws and fangs.
Eyes slitted in draconian rage.
Axe head melting at his touch.
Chainmail coif simmered down to a scarf.
Familiar purveying the carnage as a centipede.
And why defend with a shield when you can bash with it?
Next pelt's the fourth and final seasonal! Can't wait :)