I was quite impressed with this show. Sure, the plot is limited to a bunch of extremely sexual scenes and the characters don't have much depth, but Kiss x Sis is able to succeed where other anime like it have not. I've watched plenty of harem/ecchi anime and have really enjoyed some of them. However, I find that a lot of these anime fail to effectively use ecchi elements. Sometimes they'll show a random panty shot or have an unnecessary close up on a character's breasts. Such scenes are usually meaningless and fail to stimulate the viewer, which is what they intend to do, and instead end up just wasting time. Kiss x Sis actually embodies the term ecchi by being incredibly hot and exciting without crossing the border into hentai.
Plot: --/10
Some ecchi anime try to throw in a plot to go along with the fan service in an attempt to have more meaning and depth. However these "plots" usually end up being completely nonsensical and poorly composed, and instead of making these anime better like they were intended to, these oftentimes unintelligible plot lines actually make the shows worse. Kiss x Sis doesn't bother to spend time developing a meaningless story and instead focuses on making as many creatively stimulating moments as possible, which definitely works in its favor.
Art: 8/10
Keep in mind that this ova initially aired back in 2008. Even though it's older, the female characters are still more detailed and have better designs than many of the characters in newer anime that I've seen. This makes them even more enjoyable to watch when they're doing dirty things and makes me sincerely wish that I was in that lucky dastard Keita's shoes.
Sound: 7/10
The voice acting was fine, but I was really impressed with the believable moans of ecstasy and other sexual noises that the seiyuu made. The girls just sounded so cute, which heightened the overall experience for me. The theme songs and soundtrack are decent, but nothing to write home about.
Characters: 8/10
While they aren't developed as characters, the cast is still really fun to watch. Especially Riko and Ako Suminoe, the main character's sisters and the stars of the show. They both have very fun personalities and their unquenchable love for their brother is admirable. The two of them have practically all of the qualities that I'd want in an older sister (I-If I was into incestuous stuff. Which I'm totally not. Y-You gotta believe me!) They're just so great, and watching their flirtatious advancements towards their brother was an enjoyable experience. The other prominent girls showcased in this anime are also pleasant to watch and each have their own moments in the spotlight. They definitely were a positive contribution to the show. Now Keita himself if a rather plain and generic character, but that's okay, since his purpose is to be that character that the viewers imagine themselves as, so he really doesn't need to be anything special.
Entertainment: 9/10
I'd be lying if I told you that I wasn't turned on multiple times while watching this. And that's exactly what an ecchi anime is supposed to do, which is why I ended up being quite fond of this show. I loved seeing all of the dirty situations that the sisters got their brother in. There were many hot and unique ones, and it was a joy watching all of them. Kiss x Sis also managed to be absolutely hilarious at times and kept a smile on my face throughout all of the episodes.
Overall: 8/10
If extreme ecchi isn't your thing or it makes you uncomfortable, then don't watch Kiss x Sis. If you believe that a lewd animated show which was created purely for entertainment is "wrong" and "disgusting," then don't watch it and don't condescend people who enjoy it. It's as simple as that. And if you're someone who wants to watch something sexy and entertaining, I'd definitely recommend Kiss x Sis.
