Mika is a petite girl often seen wearing girly and fashionable clothes. She has long brown hair and has blunt bangs parted to the left.
In contrast to her more manipulative and cunning boyfriend, Mika is very meek and well-behaved. She seems to very gentle and caring. Mika is shown to love shopping and is generally a happy person when on dates with her boyfriend. She is shown to be very patient with Daishō and does not mind when he 'geeks' over volleyball. Mika has grown to love volleyball ever since she watched games with Daishō, and even tried playing the game with him on one of their dates.
Despite being the girlfriend of a volleyball player, Mika didn't have much interest or understanding of the sport. In fact, she broke up with Daishō just ahead of the Tokyo Spring High Representative Playoffs due to his sole focus on volleyball. However, it is later revealed that she did start to like him partly because of his passion for the sport. Unbeknownst to him, she'd attended his match against Nekoma and after seeing his determination, began to understand his interests better.
Mika approaches Daishō after Nohebi lost to Nekoma for the last representative spot to the Nationals. She congratulates Daishō for playing a great game before apologizing for calling him boring for his dedication to the sport. When Daishō is disheartened after his recent loss, Mika comforts him by praising their incredible feat of being the fourth-best team in Tokyo. She then admits that she's starting to understand his passion and asks Daishō to teach her volleyball sometimes.
After their reconciliation, Mika accompanied Daishō as spectators at the Spring Interhigh. She seems to have taken a great interest in learning about various aspects of the sport.
On one of their dates, Mika sees that Daishō wanted to play volleyball even though he had willingly promised a day just for the two of them. Mika puts her thoughts aside and willingly goes to their school court and plays volleyball with Daishō, even if it was her first time. In the end, Mika tries her best to set the ball and Daishō is able to spike it, leaving Mika with a joyful smile.
Sometime before, Mika starts dating Daishō but breaks up with him after he dedicated more time practicing. However, she seems to have felt guilty after downplaying his love for volleyball. Later, Mika attends Nohebi's match against Nekoma without Daishō's knowledge, showing that she cares about him enough to try to understand the sport. After Nohebi's loss, Mika is shown to be very supportive as she consoles him and apologizes for her hurtful words before. The two care about each other very much and soon reconcile. They go on dates often and Daishō is often careful of what he says around Mika if it's regarding volleyball, even though she said she was completely fine with it. During the Spring Nationals Daishō is still concerned about her well being, asking if she wanted to leave if she was getting bored to which she declined as she was having fun.
Not much is known about them but it can be assumed that Kuroo knows her from the past as he calls her "Mika-chan". It can also be assumed that they are on friendly terms as they have each other's number. 
- Current concern: She doesn't know what Instagram is anymore.
- Mika's name "Yamaka (山架)" comes from the name of a snake: yamakagashi (ヤマカガシ) or the tiger keelback
- When asked about them by Daishō, it's revealed that Mika has a liking towards Karasuno and enjoys watching them play.