Kanade Sakurai has a crush on Yukino, her fraternal twin sister. Yukino appears to be well aware of the fact, but seems to play it off for laughs—although she likes to tease Kanade a bit too much for comfort. Then, there is Sakuya Kamiyama, an underclassman of the two, who harbors a crush on Kanade herself. Stuff happens to them.Candy Boy started off as a gimmick one shot ONA but the notion proved so popular that more episodes have been produced. This caused some confusion with episode numbering: the first episode (the original ONA) is usually not counted, with the technically second one designated as "episode 01", etc. For simplicity's sake, think of the original ONA as "episode 00". Still, there is also a prequel, called "EX01"—and then there are the various music videos, made from scenes of the original series. Sadly the show proved Too Good to Last and ended after the DVD special (EX02). However, the story has continued in a manga, though it's more of an Alternate Continuity.
Alternate Continuity: The manga, in which Kanade and Shizuku's relation is significantly more positive than in the anime. Moreover, the manga introduces several new characters: Yurippe, Isako, Masumi, and Eri, who does not appear in the anime.
Animated Music Video: The first episode was originally a prolonged video for the song "Candy Boy" by Meilin.
Odd Couple: Despite being sisters, Yukino and Kanade have quite different personalities. For one, Kanade is much more serious and often gets irritated by her sister's ditziness, so it's amazing they get along so well.
Romantic Two-Girl Friendship: For all the yuri vibe the makers obviously strive for, the relationship between Kanade en Yukino still comes closest to this kind—although it's nevertheless a bit unusual among sisters.
Also Kanade. Yukino calls her out on it in EX02 where it's revealed Kanade came to watch Yukino swim five times in one week.
Suspiciously Specific Denial: As well as humorous, the note on Kanade and Yukino's door, if read by a passerby, would seem rather suspicious. Subverted since they really aren't doing anything explicit in their room.
Note on the door: Seriously, why won't anyone knock on the door? Really. It's not that we're doing anything suspicious, but it's common sense to knock on the door. Yes, we may be a damn shameless couple, but we aren't doing anything! There isn't much else I want to say about this, but let me say it again: KNOCK DAMNIT!!
Sweet Tooth: Yukino loves sweets... and gets constantly scolded by Kanade.
Umbrella of Togetherness: The whole plot of one episode involves Kanade trying to arrange for her and Yukino to walk home under one umbrella.
Tomboy and Girly Girl: Kanade is more tomboyish and Yukino more the girly one, though it's in mannerisms rather than appearance.
Tsundere: Kanade towards Yukino; a relatively mild example.
Shizuku depending on how you view her. She does have a tsuntsun side towards everyone except for Yukino, the sole recipient of her deredere side. However while unclear, it is hinted at that Shizuku likes Kanade and acts tsuntsun towards Kanade out of jealousy.