Tonari wa Futsuu no Nijika (chan)

Since Aira was a little girl, boys have protected her because of her cute appearance. To avoid unnecessary trouble, she decided that in high school, she'd play the the role of a girly girl.

One day, a person named Nijika, came to live in Aira's house. Nijika's family had been transferred overseas, and they wanted Nijika to stay with a family acquaintance. However, Aira discovers Nijika is actually... a boy!? Nijika who was born biologically male, wears the clothes they want to wear, puts on the makeup they want to put on, and confidently expresses their feelings without a care in the world.

Aira doesn't know if Nijika is a boy, a girl, or even her friend, but one thing is certain. Aira's extraordinary everyday life with Nijika has now started!

(Source: Shueisha, translated)

Included one-shot:
Volume 6: Rulemate