Morose Kazuki and the Apron of Temptation
With the parents of both households stuck on a South American island for an indeterminate time, they ask their children to take care of each other. Kazuki refuses to admit the dirty-minded Yuuji into the home, unless he manages to spend the whole day without doing anything indecent, so they have a competition.
Aired 16/07/2006EP 2 - Morose Kazuki and the Apron of Temptation

Tonagura!
Kazuki has been awaiting 10 years for the day when her neighbours moved back to their old house. She has a crush on Yuuji, whom she considers as her first love but to whom she never managed to express her feelings for him before they moved out. Yuuji often comes over to play with Kazuki, Kazuki's older sister Hatsune and Yuuji's sister Marie when they were kids. Her ideal depiction of Yuuji was soon shattered when he turned out more than she had expected, him acting all ecchi during their reunion. With their parents off in South America, both families must learn to live with each other and rekindle the childhood feelings they shared together. Things get even more crazy as they attend the same school.
(Source: Anime News Network)