Satomi Satō
Kotobuki is said to be "the fastest learner on how to dance" among her peers as far as her being a member of Sphere goes so much that she even guides the other three members of Sphere on dancing. Even in singing, Kotobuki is said to learn just as fast, "a pro in harmonization" according to her fellow castmate in "K-On!", Satomi Satō, and "someone who has good sense in pitch" according to one of "K-On"s staff members in charge of music.