|Relationship Status||In a relationship|
Koino Matsubara is a side character in the yuri manga Sasameki Koto. A lively and kind first year student and Mayu's best friend, who also joins the karate club. Like Mayu, contrary to Koino's cheerful appearance and attitude, she is the more level headed of the two.
- She is the only one who knows of Mayu's crush on Sumika and soon starts to develop feelings for Mayu herself.
- After she knew that Mayu was confused of what she can do over falling in love with Sumika, she encouraged her with a love advice to fall even deeper and deeper in love with Sumika.
- Strangely, after she found out that Mayu was seriously in love with Sumika, she shed tears on her way home.
- To give Mayu one more chance to prove herself to Sumika, she intended to win the karate tournament.
- No matter how much trouble Mayu causes for her, that's what makes Mayu herself, and she is contented by that, she is willing to give her courage and happiness.
- Hugging Mayu from behind she cried excited of Mayu's saying which she considers as "the most adorable things", it leaves her even more willing to cheer her up.
- The aura of her menace Yandere mode appeared one time when she hoped Mayu gives up on the president Sumika.
- Even though the karate club members were getting a break from club activities, with the senpais away on their class trip, Mayu was attending it, which made her feels jealousy.
- In the last chapter she was showing to hug Mayu against the wall, which means that she may confessed to her.