Now, I was very surprised when one of my friends suggested I should watch this - because technically, it is twincest, but its twincest done right. I personally adore candy boy, and I definately think it's one of the best animes I've seen. You shouldn't judge this anime before you watch it.
** Spoiler Alert!!! click to hide or show**
There isn't actually any sexual content whatsoever in Candy Boy - there is a kiss at the end, but you can percieve it either way as it's not really a proper kiss. Yuki has some food on her lip, which she makes a kissing face at Kana to get it off, and I don't think she really expects Kana to get it off with her lips. However, she doesn't seem to protest too much. And during the very first (originally) one-shot episode, she asks Kana for a kiss, who is a little unsure of how to react.
My favourite character throughout Candy Boy had to be Kanade, but Yuki also had a very cute personality and they are together, a couple you just don't wanna split up. There is another character called Sakuya - an underclassmen who is at first, thought to be in love with Yuki, when actually she was giving Yuki snacks in return for pictures of Kana, because she is so infatuated with her. Sakuya has many moments throughout Candy Boy where she will literally be a stalker, for example taking pictures of Kana without her knowing, taking her strawberry milk purely because it's Kanas', and lots of other little humerous things that she does because of her obsession.
The cuteness factor of Candy Boy is definately a huge part of the show; the fact that both girls need each other to get through their days together is adorable. And as said in the previous review before mine, you do genuinley either see them as very very very close sisters or an extremely cute couple. But half the time, you do actually even forget they are sisters.
All in all, an extremely lovable amazing anime, that most people should enjoy. ^_^