Up until this point, I felt that everything was still going great.

However, the revelation of Mari's plan left me feeling disappointed. That whole scene where they started to eat each other out just didn't feel credible to me. Mari had been characterised as this high and mighty person, an untouchable entity (which is why that scene with Kiyoshi and the snakes felt really funny and provocative -- because he was violating a "goddess", so to speak.) In this scene however, Mari is asking Kate to bite her tits -- like what? She is cheapening herself and behaving like a slut.

Kate's obsession with Mari also seemed bizarre to the point of being ludicrous -- I mean, stealing her underwear and dressing up as her, complete with oversized bra and wig?!

On a side note, the manga seems to be getting more and more explicit, and the author seems to be making up perverted scenes for the sole sake of being perverted, which wasn't the case before. Previously, it was just fan-service. Now it's almost like a full-blown hentai. That scene with the spinning fork was just super-contrived and lame.

...I hope it gets better, and this is not a sign of the author finally running out of good ideas, or him selling out to the crowd that just wants more sexual stuff at the expense of plot. That would be a shame.

/rant

I agree. The scene with Mari and Kate seems lackluster as well to disappoint the readers.

Sounds like it's gone into the "make it last to get more money".