Mio Akiyama (秋山(あきやま) 澪(みお), Akiyama Mio) is the bassist and secondary vocalist of the light music club.
Mio is a shy girl, and can be easily frightened, mostly due to scary stories and gross things brought up by her childhood friend, Ritsu Tainaka.
Mio originally intended to join the literary club, but is forced into the light music club by Ritsu. She gets excellent grades in school, but is bad with listening to stories involving macabre experiences, and cowers whenever something gross is brought up. While she can be mature and strict sometimes, she gets embarrassed easily, and is often subject to teasing from Ritsu and Sawako, their club adviser.
She cites that she chose bass since it is not the center of attention in the band, unlike the guitarist. Mio is more technical when it comes to music, and Yui often comes to her when she is in need of more guitar tutorials. She writes most of the club's songs, although they often contain odd lyrics. As she is left-handed, she becomes entranced whenever she sees left-handed instruments, as well as left-handed musicians.
Due to an unexpected accident in one of their live performances, she acquired a huge amount of popularity; even a fan club for her is formed (much to her dismay considering the circumstances surrounding it). Because of this, most of her classmates voted her to play as Romeo in their class play.
According to Ritsu, Mio likes watching sports activities.
Mio has a long, straight black hair and gray eyes (that are angled slightly more than the other characters). Mio is the tallest member at 160cm, and has a larger bust than Ritsu and Yui
- Mio is left-handed.
- Her surname is taken from former P-Model bassist and keyboardist Katsuhiko Akiyama.
- The kanji for Mio's name is an uncommon one that means "waterway" (Mio is usually spelled 美桜 or 美緒, from 美 - mi - "beautiful" combined with 桜 - ou - "cherry blossom" or 緒 - o - "thread").
- Mio is also seemingly a fan of Lomography, as she is often seen with a camera strongly resembling the Lomo LC-A during her summer training.
- Megumi Sokabe , the former president of the student council and also former president of the Mio Akiyama Fan club asked her for an autograph signed "Mio-tan".
- Mio tends to pick strawberry type desserts the most
- In the anime her bass guitar is a Fender American Standard Left Handed Jazz Bass 3-Color Sunburst with 4-Ply Tortoise Shell Pickguard and a Rosewood Fretboard.
- Yui named Mio's bass guitar "Elizabeth", a pun on the Japanese pronounciation of "bass" (Bass is pronounced "besu", and Elizabeth is pronounced "Erizabesu").
- Mio has the largest hands out of all the members of HTT.
- Mio is known to write the kanji for person on three times on her palm and then pretend to eat it when she gets nervous.