Ever since Hikaru's sister started middle school, life around the house has been uncomfortable to say the least. For his cute little sibling, Fuuka, went through a massive growth spurt, making her exceptionally tall with monstrous breasts to boot. What's worse, the girl is determined to have her beloved brother take her virginity and have a baby with her! Will Hikaru manage to keep his busty sister at bay long enough for her to graduate to high school?
Both of these shows are shorts that revolve around a brother and an unusual sister. Saipuu is much more sexual than Oosaka Okan, but I think if you enjoyed one, you might like the other as well.
Both shows are shorts with various ecchi scenes that feature a brother dealing with a strange sister. Cyclops Shoujo Saipuu is quite a bit more ecchi than Oosaka Okan.
Watching Jigoku Youchien quickly reminded me of Osaka Okan. The animation in both is very simple and cheap, episodes are short, and the humor is very similar.
Two of the main characters, Namika and Sakyuba, are also similar; they share a voice actress, they make weird sexual comments towards the lead males, and their personalities are similar.Although the settings are different, both shows have the same "feel"/comedy, and fans of one would probably enjoy the other.