The Arisaka sisters (Hatsune and Kazuki) and the Kagura siblings (Yuuji and Marie) lived next door when they were smaller. So close that they could climb onto each other's verandas from the 2nd floor. They would always play together until one day the Kagura siblings had to move. It's been 10 years and the Kagura siblings are moving back! Yuuji's turned into a pervert and Marie isn't the crybaby she used to be?!
This is a completed series with 13 volumes and is a comedy. There is ecchi (but what else do you expect when the MC is a pervert) and there is Romance. There was a 13 episode anime from 2006 if you want to check that out. One of the main reasons I want this is because any fan-translation/ scanlation of this that is continuing (they stopped translating midway through) and I really want a complete translation.