Mio's mother is a half British and half Japanese. Their relationship remains unknown.
Mio knows about Nozomi ever since the entrance exam as Hanabi told her. Mio routinely likes flirting with her.
Mio first meets Kazane on the day of the entrance ceremony. Mio approached and tried to talk with her. However, Kazane ran away, thus Mio stated that she loved her shyness.
Mio and Rin are on good terms. Rin believes in Mio's abilities, stating that she will not lose since Mio is the first ranked student in Setouchi.
Mio and Kotone are on good terms. Kotone respects Mio. Despite this, since Kotone is a fujoshi, she claims that she is not interested with Mio's routine (flirting with cute girls), saying that she doesn't care about girls.
Usagi meets Mio at the entrance exam. Initially, Usagi had no interest with Keijo. However, after being motivated by Mio, Usagi is willing to participate in Keijo. Usagi adores Mio greatly, going as far to call Mio as "Goddess".
Nanase knows that Mio is a former swimmer and a gold medalist. Thus, if she defeats Mio, her popularity will increase. In turn, Mio doesn't take Nanase's statement seriously, since she decides to flirt with her instead. Mio also says that she wants to hear Nanase sing in bed.
Mio meets her at the feast. When Hanabi asks Suruga to introduce her to Suruga's male students, Midori claims that they can't do that, Mio then approaches Midori, stating that it is better when it is taboo. Mio continued stating that she prefers girls instead, asking Midori to tell her name.