Hayami Mana

As Ikumi's childhood friend Mana tries very hard to convince her to dress and act as a proper girl or she'll be found out. After arguing for some time she finally convinces Ikumi to wear dresses and skirts and girl's panties. Convincing her to speak like a girl is harder.

Spoiler

In love with Ikumi for a very long time she gradually decides that becoming a lesbian for her sake is ok. It's the same Ikumi after all.