Trivia

After having seen the Japanese film Chikyû ga ugoita hi (1997), she became inspired to pursue her career as a voice actress.

Coupled with the release of her first album My Stride, Kotobuki had her first solo Japan-wide concert tour entitled Our Stride in 2012 spanning across four dates and venues starting from November 18 in Kobe's International House Kokusai Hall and ending on December 9 in Omiya's Sonic City Hall.

She previously lived in Hyogo until March 2009, and moved to Tokyo the next month, two months after the formation of the unit "Sphere" at February 15, 2009.

Born in Kobe, Hyogo Prefecture, at the age of three years, Kotobuki, along with her parents, was caught up in the Great Hanshin earthquake.

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 Sato, and "someone who has good sense in pitch" according to one of K-On's staff members in charge of music.

During her stint in both seasons for K-On!, she and her fellow cast members were involved in two live events, and just like the character she portrayed in K-On!, she was in charge of playing the keyboard in both occasions. She also played the keyboard on some of her own songs during her Our Stride solo concert tour and on Sphere's first 2013 live event, Music Rainbow 02.

At the Music Ray'n Girls Haru Choco Matsuri event in 2009, it is announced that she and other Music Ray'n affiliated voice actresses Haruka Tomatsu, Aki Toyosaki and Ayahi Takagaki will form the unit Sphere, and they released their first single "Future Stream" on April 22, 2009, and was used as the opening theme of Hatsukoi Limited.