Mako is Tomoko's classmate and Yuri Tamura's bestfriend. She has a falling out with Yuri when she decides to accept an inviation from Minami to join her group during a field trip. They reconcile; however, Yuri often remains aloof around her. Mako subsequently makes the effort to become friends with Tomoko since she seems to be friends with Yuri. As is her habit, Tomoko stereotypes this friendliness and inwardly calls her "Crazy Lesbian/Lesbo" though she will admit it is only a nasty nickname rather than a belief.
Mako is shown to be quite caring, as she felt bad for leaving Tomoko alone to eat by herself at school one day. She also feels concern for Minami despite the former's tendency to denigrate others. She initially does not seem to be that assertive and never really stands out much. However, she is not clueless. She recognizes Minami's mean behavior. When she sees Yuri behave in a similar fashion to Tomoko in front of Yū Naruse, she takes Yuri aside and politely remonstrates her. Thus far, she has not similarly corrected Minami.
Mako is always shown to have short hair, without color in the manga but depicted as light brown in a color panel. Mako is the the only character to have noticeable freckles.
Yuri and Mako eat lunch very often so it's likely that they are close friends, however that is not to say that they do not have their differences. They were having a fight before the school trip to Kyōto, which ultimately caused Yuri to be in Tomoko's group. They have since made up and continue their friendship, which has extended to include Tomoko in their daily lunches and even group texts. Yuri, however, retains a degree of mistrust and stand-offishness with Mako. For her part, Mako notices some of the bad behavior on the part of Yuri; she politely and privately confronts Yuri when she tries to embarrass Tomoko in front of Yū.
Mako initially only interacts with Tomoko through Yuri and otherwise had never directly interacted with her. In Chapter 99, when Yuri falls sick, Mako becomes overwhelmed with guilt for not having lunch with Tomoko after she mistakenly thought she saw Tomoko become dejected and start sobbing for being excluded. Viewing this as a repeat of what she did to Yuri during the school trip, she begs for forgiveness from Tomoko. In reality, Tomoko did not care, which she tries to explain to Mako. Thinking Tomoko was lying to spare her feelings, Mako becomes convinced that Tomoko is a good person, and makes Tomoko her friend. For her part, Tomoko starts to inwardly refer her as ガチレズ (gachirezu) which most English translations render as "Crazy Lesbian." レズ does mean "lesbian." ガチ , as the link explains, can mean "serious," and "in earnest." When she next talks to Mako in Chapter 112, Tomoko inwardly adds the honorific san to her personal nickname for Mako, and uses it again in Chapter 129.
Minami and Mako are casual friends. Minami invited Mako to her group for the school field trip to Kyōto and additionally invited Mako to eat lunch together when Yuri was sick from school. In Chapter 129 when she sees Minami alone and crying at the amusement park, she decides to accompany her. When Minami receives texts from Asuka Katō indicating that Akane Okada is sorry for their argument, she tries to encourage Minami to return. She later stays with her when Minami refuses. However, she does not challenge Minami over her mean-spirited gossip as she did with Yuri.