I'm looking for the title of a manga in which a boy wishes for a sister for Christmas. Years later a "santa" gives the now grown up boy a kid sister saying its his present from years ago.
Thats the best i can remeber of the description.

Chokotto Sister?

Chokotto Sister. haven't read it yet, but sounds interesting.

I'm guessing Chokotto Sister as well, but its really really good. Although underage nude scenes are a bit meh, they don't add the lolicon sense to it.