Tsuyoshi Ohki is friends with Akito. They are very close and he seems to be the only person besides Sana to understand him.
In the 6th grade, he and Akito became best friends with Sana. Following their friendship, Tsuyoshi made it clear that he had a crush on Sana. However, these feelings were not returned. He is one of the not-so-main characters.
Tsuyoshi lived with his mother, sister, and father. However, when his parents divorced, he moved to an apartment along with his mother and sister and had to take on the role of being the male in the family, forcing himself to be strong and not show his tears.
When made angry, Tsuyoshi goes into anger fits which only Akito can stop. This is first seen when he calls his teacher "mommy" and all the children make fun of him. In embarrassment, he becomes mad and starts destroying the classroom.
When he meets Sana, he has a crush on her. When Akito asks him if he really likes her, he confirms it. This results in Akito claiming Tsuyoshi as his rival.
When Sana's friend Aya, confesses to him, Akito tries to persuade him to like Aya and not Sana. However, Tsuyoshi knows what he is trying to do. It is then revealed that the reason he likes Sana is because she gave him Valentine's Day chocolate in the 5th grade. By mistake, Sana had given him one that had been left over. Now realizing the truth, he becomes hurt and angry and so, he goes into one of his fits. Eventually, he and Aya start going out and they are known as the lovey-dovey couple.