I'm definitely in the minority here by giving this a poor rating, but personally I don't think this game is actually that great.
First of all, the art is fantastic, the music is great, and it's clear a lot of effort was made by the people who worked on this game to make what they believe to be their best work.
However, I think the gameplay for SiniSistar is really lacking. Nothing ever changes the whole way through, and your mobility and combat abilities are seriously limited. I got through the entire game by hitting the enemy in front of me, jumping back, and repeating until the game was over. Also, all of the areas in the game are incredibly linear and don't offer much in the way of choice aside from whether or not you want to die or not. The platforming is a joke and rarely do you actually need to do precise platforming in the game.
Almost all of the H content is pretty disgusting to me. If you're a fan of spiders, maggots, and beheadings, this game is perfect for you. Personally, not a fan. I was expecting something like Night of Revenge where there's a lot of fucked up shit but at the end of the day there's still lots of fucking and it's hot, but this game really focuses on things that I can't see the appeal of. Do people have a fetish for zombies eating people? Don't even get me started on the bugs.
Overall, I think the art is fantastic and the game feels like effort was put in, but in the end I think the gameplay and sexual content both are extremely lacking. I would feel bad rating it this low if others hadn't already rated it so highly. Definitely give SiniSistar a try for yourself, maybe you'll be into it.