Her bass guitar is a left-handed Fender Japan '62 Reissue Jazz Bass in 3-Tone Sunburst, and she usually plays with a pick. It gets named Elizabeth by Yui. In Japanese, since "bass" and "Beth" are both pronounced as "besu", this results in a pun where the name can be interpreted as "Elizabass". Initially Mio dislikes this name, but comes to like and accept over time. She uses D'Addario EXL160 strings on it, though they are incorrectly shown as EXL160M strings, even though her bass is not a medium-scale. There is a medium-scale version of Mio's bass, but it is only made as a right-handed verison. Fender Japan's page for the JB62/LH.
In the manga, Mio also owns a Fender Precision Bass in the same colors as her Jazz Bass. This was her first bass and she played it until she acquired the Jazz Bass between her second and third year of high school.
Mio is left-handed. She was made left-handed because the manga's author, Kakifly, is also left-handed.
Her surname is taken from former P-Model bassist and keyboardist Katsuhiko Akiyama.
The kanji of Mio's given name (澪) is uncommon and means "waterway" or "channel". The given name "Mio" is usually spelled 美桜 or 美緒, from 美 - mi - "beautiful" combined with 桜 - ou - "cherry blossom" or 緒 - o - "thread".
Mio seems to be a fan of Lomography, as she is often seen with a camera strongly resembling the Lomo LC-A during Ho-kago Tea Time's first summer trip. (This is only shown in the anime.)
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" after being amazed by Ho-kago Tea Time's surprise private concert for her.
Mio tends to pick desserts with strawberries the most often.
Mio has the largest hands out of all the members of HTT, which is very useful for a bassist.
Mio is known to write the kanji for person three times on her palm and then pretend to eat it when she gets nervous.
Though Mio is the most mature in appearance (and in the way she acts), her personality can also be considered the most child-like: she cries a lot, she's known to be a scaredy-cat, and the lyrics she writes are cute, childish, and 'fluffy' (e.g. Fuwa Fuwa Time).
Mio can be regarded as the female counterpart to Paul McCartney of The Beatles. Much like McCartney, Mio is a Left-Handed Leading Bassist who has a penchant for writing sickeningly-sweet and cute lyrics, despite of being the sole voice of maturity and reason within her band that is obsessed with (unsuccessfully) maintaining order and discipline. Mio also shares a close if argumentative friendship with Ringo Starr's counterpart Ritsu (much like how McCartney was to Starr), and also lifted her friend's spirit out of depression (in college) with the heartfelt use of a postcard.
Also, much like McCartney, Mio is a left-handed bassist who taught her band's idiot savant Yui (Ho-kago Tea Time's equivalent of John Lennon) how to play the guitar from scratch, and both routinely share lead vocal duties with the idiot savant of their respective bands.
Mio appears to have a guitar pick but has never been seen to actually use it.
Her guitar pick can also be seen in the opening and ending themes of the anime, though she is never seen using it too.