Kiss X Sis is one of the most surprising manga I've ever read. What is surprising about it is how trashy, sleazy, and exploitative it is. Depending on your point of view, the incest is already pretty trashy. If you're not okay with the concept of two step-sisters lusting after their younger brother, then you probably shouldn't even come close to this manga. Don't touch it with a ten-foot pole.

Story: 1/10
As I said in the introduction, this is one of the most sleazy manga I've ever read outside of actual hentai. I get the feeling that the author doesn't know what he's writing, because the manga plays the entire thing for pathos and/or sexiness despite some pretty exploitative stuff being away a couple pages away. Sex is a huge part of the entire enterprise, but it can get pretty messed up in regards to that. If the incest wasn't screwed up enough for you, there are multiple depictions of urine and/or vaginal fluids played for sexiness (I guess), several scenes where characters are implied to masturbate, erections depicted through pants, and one attempted rape scene. Again, this entire thing is played for pathos which is completely destroyed by the cringe-worthy scene you've just read a few pages ago. It's an manga where the words "this is so wrong" are repeated several times in your head as you read the thing. Those with strong stomachs will be able to make it through without quitting the entire enterprise, but those who can't take it should stay away. It's completely and utterly shameless, but not in a lighthearted way, or a comedic way, or a clever way, or an ironic way, or a dark way, or even a good way. It's shameless in an exploitative way.

Art: 4/10
Despite it's sexually explicit content in regards to situations, this is an manga that really contains very little nudity or fanservice. Compare it to something like To Love-Ru Darkness or High School DxD, and the difference is clear. I have a theory that if it were like that it would be slapped with an 18+, but it's strange how restrained it is in the nudity regard. Those looking for naked girls should look elsewhere. That said, the art isn't great. It's highly simplistic, and can border on amateurish at some points. Still, it does its job well enough to give it a 4.

Character: 2/10
This is a harem anime, so lets talk harem protagonists. Keita Suminoe is basically what would happen if you crossed Makoto from School Days with Kasuga Arata from Trinity Seven. He's a realistic depiction of a teenage boy in that scenario, but in this case the teenage boy is kind of a two-timing jerk. He's not entirely bland, but he's certainly not a character who you can imagine a girl falling head-over-heels in love with him. Alright then, let's talk haremettes. His harem, save for one character, is a collection of thirsty hormonal women that can get pretty annoying at times. The only one you really want Keita to get with is Miharu Mikuni. She's the most likable person in the cast, and is pretty much a one-dimensional big-breasted meganekko stereotype.

Enjoyment: 3/10
I said that this is a manga where you can't help but repeat the phrase "this is so wrong" in your head. Well, that's for certain scenes. A lot of this manga is played for pathos and drama, and since the characters range from unlikable to bland to annoying it won't affect you in the slightest. Outside of some of the hilariously awful lines ("Why is incest everywhere?") that make it worth the read, it's rather a rather bland, boring, and often annoying waste of time.

Overall: 3/10
Skip it.