I say Kotobuki and two person will come on your minds that are closely related. There is K-ON's Kotobuki Tsumugi, the fluffy, air-headed lady keyboardist of Houkago Tea Time or HTT for short. And of course, her seiyuu that gave life to her, Kotobuki Minako, the youngest but very mature for her age, member of Sphere.
Prior to her debut as a seiyuu, she already has done some acting works gaining acting experience. At the young age of 14, she got a role on an independent film. There follows a lot more independent films she took part in. She loves acting, and pursuing a seiyuu career was due to the inspiration the film "Chikyuu ga Ugoita Hi," brought to her. Together with fellow Sphere member and seiyuu, Toyosaki Aki, they had their seiyuu debut role at the anime "RED GARDEN" playing the part of a background character. In 2009, her first major role came. She voiced Rika Dobashi of "Hatsukoi Limited." Also, as a member of Sphere, their debut song "Future Stream" as used as the opening theme of the anime. So far, her most notable role is Kotobuki Tsumugi of K-ON! As they have a lot of similarities, fans see Minako as the real life Mugi. Even she herself admitted that she felt she most closely relate to Mugi compared to her other characters.
Suggested Must-see Roles
Shidou Misaki (Sofuteni)
In search for a villainous voice of Minako? Then you should see Shidou Misaki. Though Misaki is just a supporting character, she's a very enjoyable character because of Minako's portrayal. She voiced her with the usual cuteness but with the addition of that cool evil-like voice. And also, on Sofuteni, her partner in crime and the character that she bullies, somehow, was voiced by Toyosaki Aki which makes their combi funnier.
Daidai (Otome Yokai Zakuro)
This is a must-see for Sphere fans, especially Minako and Haruka fans. Daidai is also another antagonist character voiced by Minako, and supporting too. But what made this a must see for Sphere, Haruka, and Minako fans is due to three reasons. Firstly, the anime used Sphere's Moon Signal. Second, Toyosaki Aki voiced a major character on the anime. And lastly, Tomatsu Haruka voiced the older twin sister of her character. Daidai is a weak, jealous character while her twin sister, Byakuro, is a strong intelligent character that loves her sister very much, Haruka and Minako did a great job voicing them on their dramatic scene at the last episode. That scene is a little heartbreaking for those who admires their friendship so much.
Dobashi Rika (Hatsukoi Limited)
If you're looking for a boyish character from Minako, then Dobashi Rika must be the first you should check. As it is her first major voicing roles, it put K-ON! fans, who have seen her Mugi first before this one, in awe. She voiced Mugi with a very lady-like voice. On the other hand, she voiced Dobashi in a cool boyish way. You could say it was with a bit cold tone.
JInguji Yako (Chu-Bra!!)
Another boyish character voiced by Minako though lesser. This is a suggested must see for K-ON! fans as they will get to hear Mugi and Mio's voice fighting.
1. Smile I have entitled this review with "The Smiling Voice" for this reason. A smile can be felt upon hearing her voice as it can be very lady-like and girly. One example is her most notable role, Mugi. Then, another is Kanzaki Mizuki, Nishi Yuko, Toto (Coicent), and HIjiri Yamaguchi (Kyoran Kazoku Nikki).
2, Kansai-ben (Kansai Accent) Nabeshima Nekomi (Medaka Box) and Nishi Yuko are examples of her characters which required her to use her Kansai accent. Minako grew up on Kobe which is part of the Kansai region so she's very fluent in it. Most people says her Kansai accent is cute.
3. Cool Sarcasm She usually sounds so nice and innocent, so hearing her being sarcastic souns really good and cool at the same time. And I think tsundere roles would fit her too. Examples of the characters she voiced this way are, karina lyle/Blue Rose, Mitsuko Kongou (To Aru Kagaku no Railgun), Sen Tokugawa (Hyakka Ryouran Samurai Girls), and Takahi Ninomiya (Kakumeiki Valvrave).
Dream Role
Tsundere Characters She hasn't done much tsundere roles, and as I have mentioned there, when she sounds sarcastic, it feels like it would fit a tsundere character.
Romance Genre Anime She doesn't have much roles involved in this genre. So far, there's Dobashi Rika, and Toto of Coicent.