Mitsuo first appears as a girl named Miyu, who quickly becomes friends with Seto. It was revealed that crossdressing is a tradition in his family, and that he was in fact male.
He's the most minor of the main characters, until the end of season one, where he plays the role of deuteragonist. It is revealed that his brain can't produce chemicals necessary for romantic attraction. This is cured by Josh Hīragi, however. Thanks to Oto Kagemaki, Josh and Mitsuo form a romantic relationship, and he helps in the fight against Beatrice. He decides to return to America with Josh, and they are set to leave at the end of episode 25, and return at the end of the filler arc that will begin season 2.
A headstrong girl(?) who isn't one to give in easily. Miyu is also very smart and good with weaponry and knows martial arts.
Miyu's aura consists of light blue and yellow translucent dots, multicolor stars and flowers, and yellow and purple clusters of candies and pearls.
- They are known as RA's 2nd generation "Sin Patroller".
- It's a running joke for them to get kicked out of Yuki and Sakutaro's house.
- Though thought to be a girl, there is no evidence besides their hairstyle and clothing to prove this, as they have a completely flat chest, wear baggy clothing which conceals anything of use for gender identification, and speak in a boyish mannerism. They do indetify themselves as female, but it's nit confirmed.