Chocotto Sister

Haruma Kawagoe has had the lifelong wish of being an older brother. However, after a miscarriage and an operation, his mother could not give him a little sister. Nevertheless, he never gave up on his wish.

One Christmas night, during his college days, Haruma has a huge present delivered through his window by a woman on an airborne motorcycle claiming to be Santa Claus. The present contains the little sister he always wanted, and Santa justifies the time it took to fulfil his wish by saying that making a little sister takes a lot more time than just making an android.

This cute manga and anime follows Haruma's life as he attempts to adjust to suddenly having a little sister out of the blue, especially a little sister who has an instruction manual with material inappropriate for her age, and follows it religiously.

Tropes this show has examples of:

 * Accidental Pervert: Inverted in episode 4. Makoto pushes Chitose into Haruma's apartment. Poor Haruma, he was only wearing a towel.
 * All Love Is Unrequited: Taken to almost absurd levels - literally every single character except Choco is in love with someone totally oblivious.
 * Bottle Fairy: Makoto, one of the tenants where Haruma is staying, who also loves to tease their landlord.
 * Childhood Marriage Promise: In the manga,.
 * Christmas Episode
 * Cloudcuckoolander: Chitose has a rather vivid imagination
 * Crowning Moment of Heartwarming: The anime's ending.
 * The ending of the manga actually raises this by a few degrees.
 * The second half of episode 12 certainly qualifies.
 * Cosplay: Not so much in the series proper, but the below-mentioned Dancing Theme is obviously aimed at cosplayers--and not without success.
 * Dancing Theme: Neko Nyan Dance, anyone?
 * Defrosting Ice Queen: Yurika.
 * Erotic Eating: Done by Choco with a chocolate-frosted banana
 * Eyes Always Shut: Tamami
 * Extreme Doormat: Chitose.
 * Fan Service: Quite a bit of it
 * Fluffy Tamer: Choco, with Kuro the panther.
 * Furo Scene
 * Girl in A Box: specifically, a little sister delivered in a present. Oh, and it's a bag, not a box
 * The Glomp: Choco loves doing this to Yurika.
 * Growing the Beard: Hang in there. The show does get better in its run, and not by a small margin either.
 * Hadaka Apron: worn by Choco at one point because her manual says that older brothers love this sort of thing.
 * Hot Springs Episode
 * Kawaiiko
 * Landlady: Chitose
 * Lovable Sex Maniac: Makoto, although she tends to go a bit far in her teasings at times.
 * Meganekko: Chitose
 * Meido
 * Moe
 * No Social Skills: Choco has no experiences in life at all, and relies entirely on her inappropriate manual.
 * Ojou: Yurika. Her home is huge.
 * Ordinary College Student
 * Panty Shot: To the point of ruining a very emotional scene.
 * Promotion to Parent: Choco's arrival forces Haruma into this. Luckily he gets a lot of help (?) from his neighbors.
 * Put On a Bus:.
 * Santa Claus: Well, a Santa, if not the actual old cheerful man.
 * Shouldn't We Be in School Right Now: One should worry for Choco's future, seeing as she never gets any education.
 * Shout Out: One of the last chapters features a picture of Yotsuba&!'s main character Yotsuba on a milk carton.
 * Tear Jerker: When Haruma's mother is hospitalized, and tries to tell her son that she can't give him the little sister he wanted
 * And then there's the double whammy of and Choco's encounter with.
 * In the manga,
 * Theme Tune Cameo: The ending theme, Neko Nyan Dance, is the Dancing Theme of an in-universe children's TV show. One episode centers around the apartment residents making a video of themselves performing the dance.
 * Tsundere: Yurika, voiced by none other than Rie Kugimiya.
 * Tsurime Eyes: Hideko, Yurika's maid, sports them.
 * Not to mention Yurika and Makoto.
 * Undead Tax Exemption: Choco's appearance somehow doesn't cause any problems.
 * Unfortunate Implications: Choco's manual seems to full of information that you'll enjoy or be repulsed by.
 * What an Idiot: Haruma in the anime version,
 * Also Choco herself when it comes to Kuro.
 * Why Do You Keep Changing Jobs: Tamami.
 * Zettai Ryouiki: Yurika.
 * Why Do You Keep Changing Jobs: Tamami.
 * Zettai Ryouiki: Yurika.