Fushigi no Mayuri-san

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)