I feel like Erina would fit in with Akane and Sumomo. So here is a drawing with all three of them.

This led me to redesign Akane since her hair color used to be similar to Erina's. Akane's hair color now kind of looks similar to who she was inspired from, Asuka Tenjouin from YuGiOh! GX. I hope there is a way to fix this.