Ryoko Kanou
Ryoko is the girl that has a passion for painting, as we see her, in her off time, drawing or painting. Ryoko is also a neighbor of Tsuyoshi in the apartment complex they are living.
Her episode is episode 4 where she asks Tsuyoshi to be her Apollo model for a drawing. First, Tsuyoshi models in her apartment, but later, to finish it, she asks him again to model for her in the school. This will lead them into a strange situation, later.
She only makes a cameo in the OVA, in the intro, where she is making, you guessed it, a drawing.