Tsubasa Sumisora Edit
He is actually very kind to Tsubasa, treating her extremely well as shown in episode 1.
Momotaro Onzai Edit
He is best friends with Onzai, and has a very close relationship with him. He also knows about his ability to see spirits shown in episode 6.
It's been hinted many times that Mikado may think of Momotaro more than just his best friend. In episode 6 of the anime, after Goushi showed his concern for Momotaro, Mikado told him that he won't let Goushi take Momo away from him.
In 2D☆STAR Vol.3 interview, MooNs did an anonymous voting for the question, "If you were a girl, which of the members would you want to date?" However, Mikado willingly revealed that he votes for Momotaro and wants to see Momo's face when he knows it's him. He also challenged the other rival to come out and show himself.
Kazuna Masunaga Edit
Mikado is very fond of Kazuna, and the two are band-mates.