|Hair color||Dark gray|
|Friends||Tanaka, Raku, E, Tsuji, Azuma|
|“||Raising a flower that will surely hurt someone||”|
Tanaka & Yamaguchi
She wears a gray gakuran top with orange-red jersey pants. She has what seems to be a jacket tied around her waist backwards. She wears a white undershirt, although it is not usually visible. The ribbon on her uniform is not tied. She wears white school slippers with her name written on them.
Her eyes are black and her hair is dark gray and worn in bob-cut pigtails, which are tied with small ribbons. Her skin from the neck down seems to be all black. She has wolf-like ears that seem to be pointed upward when compared to Tanaka's.
Yamaguchi is a girl who appeared in the Saikyouiku PV. Not much is known about her past, except for that she and Tanaka may have been bullied in their childhood.
She may have fought in a war, as seen in the chorus, where she and Tanaka threaten/kill dreams with a "selfish knife" and "sophistic justice". The lyrics state that their loneliness won't heal, and that they are unable to figure out real happiness. They also cannot see a better future for themselves.
Aside from that, she is known to very active. It also seems that she has an eye on Tanaka. She also loves potato chips. Although she can be hotheaded, overly honest, and blunt at times, she really cares about her friends, especially E and Raku. She uses a knife as her weapon.
- Her race is not confirmed yet.
- A speculation is that Tanaka and Yamaguchi are half-youkai (半妖) due to their dog/wolf ears and skin color.
- Another theory is that they were originally human, but experimented on to give them wolf-like features. This theory has support, as (assuming that the Neru songs all took place in one universe) E may have been a fellow experiment (although given robot parts instead of animal parts).
- Once on one of Sidu’s drawings, Yamaguchi was opening a bag of potato chips and it exploded.
- She really cares about E's health.
- She seems to know Tsuji, as they went to the beach together. We can assume she knows Azuma as well.
- She is right handed.