Description from GANMA! :
Yuusuke, a 7th grader, is interested in his friend's older sister for various reasons.
The older sister, while a little strange, is a kind and caring girl.
She's mysterious, but is popular with everyone.
This is an ordinary comedy about Mayuri-san's mysterious everyday life.

Author/Artist’s Twitter: https://twitter.com/panzuban (Though it seems they do not/have not posted much about this comic)