Number 11 of UQ Holder's immortal squad, Numbers. A 14 year old who comes from a tribe of demi-humans (Yatagarasu) where children are born genderless, but can choose to become male or female during a ceremony on their 16th birthday. Kuroumaru currently wants to become male, and thus identifies as and presents himself as a boy. He has romantic feelings for Touta, but denies it to everyone who points it out, claiming he only wants "male friendship" with Touta. He is a practitioner of the Shinmeiryuu, a sword style also seen in Ken Akamatsu's previous series.