>>90060747Usually subtle sexuality makes your dick the hardest. Sora and Mito being just normal human girls makes the tension subtler and "more attainable" (closer to the home, so to speak). Also worth mentioning, as anime-styled characters, technically, they are "perfectly" attractive nonetheless, as in imperfections of real women don't pertain to their images.
All of that interplay just makes your brain go wazoo.