Some minor spoilers ahead:
Okay, I'm going to start off by saying this is my first review and I am only actually doing this because a lot of the other reviews are kind of harsh and don't take something into consideration. Now, I consider myself pretty open minded and watch a good amount of ecchii and harem comedies so its not like I get surprised very often, but this one did catch me off guard, in a good way.
*~Story~*: This...is pretty basic and bland for the majority of the series. Its so cookie cutter, I wouldn't normally consider giving this above a 6 usually and I would say other's reviews are justified, HOWEVER, this did something rather unique. You have the incestuous sister, 3 additional heroines who have no real story of showing up except to suddenly be there as a way to get into the sister's way of pursuing her forbidden love and eventually even the teacher who seems smitten for the MC for no other reason than she just has to be to lead him on a proper path. Jokes ensue and its really nothing special from whats ever been done before, except...the ending. The ending had a couple of hooks in it that I found very novel and I will admit I was surprised and didn't see them coming. You find out there ARE deeper motives to these girls that had supposedly just shown up and there is more to just falling for the MC just for the sake of plot. To me, the ending is a very integral part of the show, there have been very many that were fantastic and really superior only to drop the ball at the very end. This is a rare exception in where it did the total opposite. The ending actually redeemed the rest of the show, it made the previous 9 episodes or so of watching it worth it.
Story score: 8. I'd rate this higher if there was some notable things throughout the story, but as highly as I rate the ending its not everything, especially when you might lose most your audience before they even get to see it.
*~Art~*: This is cute. While its not spectacular by any means, nor does it particularly have anything to make it take itself serious or engaging, the characters themselves seem oddly disproportioned/designed. This isn't really a bad thing though, it really fits with the easy going nature of the show and are easy on the eyes. Each of the characters is distinct save the MC himself who is made so painstakingly generic it can only be done on purpose.
Art score: 7
*~Sound*~: This is probably the weakest part of my review because if I am honest, I don't have much of an ear for music. That said, nothing stood out to me nor did anything particularly bother me, I didn't even think of it at all as I watched. Leavening me to say it left no impression either way.
Sound score: 7
*~Character~*: Okay, this is where a show like this is usually made or broken. I mentioned that many of the girls just pop up with no real purpose, love the MC for no real reason, and frankly are...very typical. There is nothing about them that should make this particularly stand out, however I don't want to give anything away, but the ending reveals a depth to them that is not at all apparent through the majority of the show. The are mainly eye candy and there to compromise the MC's standing with the little sister and pursue deviant like activities with the protagonist because...plot. The main issue I have is that there is no real depth or unique traits to any of the heroines unitl...said plot device happens. It actually happens so abruptly and without actual warning, I can't help but feel it was just kinda added as a last minute idea and as far as that goes it was a great one. The characters are mildly funny and each is great in the delivery of the role they portray keeping this rather simple and easy to enjoy
Character score: 7
*~Enjoyment~*: This is a very simple comedy/ecchii, you don't have to think too hard about. Its not going to really stand out as a great title, but its something that is a nice break when you are on a horror/suspense binge or perhaps just need a comedy with a bit of sex appeal to it. I personally like titles like this since I am all over the board with what I watch, and some shows can be very emotionally draining, so a simple comedy with pretty girls to look at is nice. I know I keep harping on it, but I was floored by the ending. As someone that watches a lot of ecchii/comedy/harems and still being took by surprise was quite novel, and I enjoyed the reason behind the girls that much. As pointless as it started out to be, the ending gives you a very good clean up of it, but only if you're the type that will be patient to get that far in the series.
Enjoyment score: 8
Overall: I gave it an 8. Many people are right, this show is pretty lack luster, but its simple and you can turn your brain off for it. Its not something I'm gonna say people need to rush to go see, however, it offers a unique take on the harem genre I found refreshing. So much so I at least decided it didn't deserve all the harshness a majority of the reviews say. You won't be missing much by passing on this, but I can't help that this title got wasted somewhat. That ending brought together such an intriguing plotline to it, it feels like the mediocrity that lead up to it doesn't do it justice and that with better planning or story management, this could have been a very epic anime in its own right. Sadly, one great idea is useless when nobody will get to the point to appreciate it because of tedious/poor lead up.
If you want ecchii/comedies that might stand out because of being slightly beyond the norm and have better story throughout, I suggest to try
Rokujouma no Shinryakusha or Boku Ha Tomodachi Ga Sukunai