Mugi first met Yui back in the light music club room and had spoiled Yui with sweets and drinks so that Yui would be interested to join the club. After joining, Mugi had done quite a lot of good work for Yui, such as lowering the cost of the guitar that Yui wanted to buy.

Yui has always liked Mugi's cakes and cannot not wait to eat them. It is said that, without Mugi's snacks, she would not be able to play the guitar properly.

Like Mio, Mugi is very concerned about her weight, and will get very annoyed when Yui talks about her fast metabolism.