Mimika is a blonde Long Arm similar in appearance to Gardenia, with the only noticeable differences being the white tattoos under each of Mimika's eyes and a noticeably happier expression.
Mimika is a solo player, and has learned how to play without relying on other people. She is incredibly strong, able to take out even high level monsters with just a few blows. Due to the fact that she's controlled by multiple people, she appears to constantly talk to herself, and refers to herself as "we". Her voice also changes. This can be confusing for those who aren't aware of the circumstances of her players in the real world.
Mimika was actually controlled by three girls in their final year of high school named Mirei (美零), Miruko (美留子), and Misaki (美咲). They shared the belief that they grew to become uninteresting girls that weren't special in any way and felt that if they'd all created individual characters, they wouldn't be able to progress very far in the game, so instead they took turns playing Mimika. When they began raising Mimika, the three promised to give their all in their cause until graduation. With Mimika being played almost constantly they were able to get her up to a high level. As graduation came closer they realized that they wouldn't be able to play together anymore, which helped guide their decision to sacrifice Mimika to save Mimiru's old PC and her friend.