I'd agree with you only if they were adults who negotiated a scene. They're high school girls and the only reason why the blonde is even participating in this is because she's attached to the black haired girl enough to let her do terrible things to her. This isn't just some consenting kink play performed after school, it's a girl abusing her friend simply because she wants to see her suffer, the black haired girl was even mad during the age play chapter because the blonde wasn't suffering like she wanted. She's only doing this because seeing her friend suffer at her hands turns her on.
abuse and kinks are very different things
Okay but this is a story about abuse. Whether or not people enjoy the kinks depicted doesn't matter.
For those of you who say this manga is disgusting, you probably don't like it because of the unique kinks/fetishes featured in it. People like different stuff. A few of the fetish/kinks I have seen so far in this manga are:
-Emetophilia (Vomit Kink, you like watching people vomit)
-Ageplay (Baby/Mommy kink, you get aroused from acting like a child or treating someone like a child sexually. Usually some humiliation/BDSM elements mixed in)
-Piercing fetish (Lumped in with tattoos as well, you either get off from the act of piercing/tattooing or from seeing them on yourself/somebody else)
-Pee Fetish (You get off from watching someone pee or soil themselves)
And of course a bunch of other BDSM stuff like domination/submission, spanking, blindfolds, etc. The stuff they do is honestly BDSM roleplay almost with Ari being the female dom and Hina being the submissive. Although there is some dubious consent involved and some violation of public decency as they are technically enacting their sessions in a public space(school), they are for the most part not doing stuff that is 'disgusting' or 'immorally wrong' per se. They are just exploring their sexual behavior through sexual acts that are considered 'not normal' to the vanilla society.
All in all, if you think this manga is disgusting that just means you probably don't like the kinks involved which is fine. To each their own. Just please don't degrade a work that the author-sama spent so much time on because it doesn't fit your palette.