Mimuro (三室) and Hotarubi Mei (蛍火名)
First introduced and last seen in volume 5, Mimuro and Mei seem to share some similarities with Soubi and Ritsuka: they are an adult/child team, and the child is feisty and insecure. Mei dresses boyishly in the beginning, but during their battle with Soubi and Ritsuka, Soubi takes off Mei's cap and after the fight, Mei has a tearful argument with Mimuro about whether he prefers boys or girls. (She thought boys, apparently she was wrong.)
Their markings are on the backs of their hands.