With Kiss x Sis the basic plot is that Keita's older step-sisters, Ako and Riko, are in love him in a very lustful way. At first Keita dislikes the thought of seeing them other then brother and sister. However during the time that Keita is studing hard to get into the same school as his sisters they do their best to help him out in very naughty ways. Add in the hot Otaku teacher that thinks the idea of her students getting it on with their brother is a bad thing but finds her self lusting after the boy herself and don't forget his large breasted classmate who has a problem finding the appropriate time to use the restroom. Keita also has a few friends that give him shit for being the girl's brother and getting to play with his sisters all the time.
There is a lot of fanservice and ecchi moments and it only gets better as the series goes on. It doesn't go full on or have any nudity (for the TV release) but it definitely doesn't leave much to the imagination. Keita with the lusty help of his sisters is able to get into their school and all is good with life in the end. This is probably not an anime series that will find it self licensed in America due to the nature of the relationships but you never know. I am though surprised at the lack of fan-made art out there. There's only three pages of the stuff on Danbooru.
I couldn't find a trailer for the show so you'll just have to make due with the opening video instead...
