Котобукі Цумуґі

Tsumugi Kotobuki, otherwise known as Mugi is one of the 5 main characters in K-ON! She is a wealthy, cheery, cute girl with a gentle personality who plays the keyboard and is the main musical composer in the band Ho-kago Tea Time.

Mugi plays a Korg Triton Extreme 76-key keyboard, though she is also seen playing a Korg RK-100 keytar in the closing credits of the first season.