In my opinion, this story is centered around Marin Kitigawa, and she's a wonderful character.
She is not only the heroine who accepts Wakana Goujo, but she's the person whom we see grow the most out of everyone in the series. She props Wakana up, telling him to not let himself be taken advantage of. She's an obvious free spirit who is comfortable in her own skin.
But here's what is incredulous to me.
Marin is 15 years old. She's in the "she should know better" chapter of teen life. She's not very modest-minded in her choices of clothing. What she wears is very revealing --- and she wears it anyway. There isn't a 15 year old girl on this planet who is not conscious of her maturing body and the attention she might draw by wearing certain clothing that spotlights it. I didn't buy that as her simply being innocent at all. She is depicted as having a "heart of gold". And that really is the defining characteristic of Marin's personality. She always means well, and is unaffected what others think. But --- her unabashed self-sexualization is actually a very, very unbelievable part of the story.
Don't misunderstand. I really love Marin's character. She's a very sweet, down-to-earth girl. And watching her organically discover her feelings for Wakana felt refreshingly genuine for this genre of anime. The fact that she did not see their partnership as disposable is one of the strengths of Marin's personality. On that merit she's a refreshing high-school anime character.
However, her lack of modesty in dress clashes with her bright personality. To me? The author went very thick on the fan-service just to grab everyone's attention. Marin's obsession with eroge, S&M, succubi and the like could only come from a dark, cringey place. Therefore her passionate hobby steeped in those dark characters could not take root in the sunny heart of someone like Marin Kitigawa. Not without presenting heavily in her personality.
As a valid example? Within every manga or anime featuring boys steeped in that same material, they are all vile, cringey, sex-obsessed perverts.
I guess what I'm saying is there is a major clash in who Marin IS and what she LIKES. And that's wholly impossible to believe.
[I actually intended to give 2.5 stars, but I can't seem to correct it.]