Kotoha is Arata’s childhood friend, even though her family the Uneme clan has served the Hime clan for years. She doesn’t understand that Hinohara isn’t the same Arata that she knew all those years. Instead she just thinks that he lost his memories after being “eaten” by the Kando Forest. She has the power to heal which is a power that all woman of Uneme clan have. She tags along with Arata and brings him his Hayagami, and she will go where ever Arata Hinohara goes.

(Source: Wikipedia)