If you liked the Cyclops Shoujo Saipuu anime, the Anime-Planet community thinks you'd like:
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.
Both series have short scenes with often fan-service content. While Oosaka-chan is more reserved about the amount of fanservice Saipuu doesn't even bother with subtle moments at all.
As siblings go, Atsumi and Atsushi are anything but typical. High schooler Atsumi is exceptionally small for her age, and elementary schooler Atsushi is abnormally tall with a deep voice, leading to misunderstandings on both sides! Whether Moriyama-sensei gets embarassed by Atsushi's every move, or Atsumi is offered candy meant for children, or poor Atsushi is arrested for being a perv that’s trying to snatch kids on their way to class, this brother and sister duo is bound to have an eventful day-to-day life!
Two very short shows dealing with unusual sizes and siblings. Recorder to Randoseru has an older sister who is abnormally short and a young brother who is abnormally tall, while Cyclops Shoujo has a younger sister who suddenly grew due to puberty. Both include comedic skits with no real plot, so if you liked one, you may enjoy the other.
Short and episodic, both are about siblings with different personalities going through everyday life occurances. While Cyclops Shoujo Saipuu is by far the more perverted of the two (The only one that's perverted), they're both episodic and formulatic, keeping things mostly at status quo when the credits roll.
Both short series are about siblings who are very different from each other as they go through everyday occurances. Cyclops Shoujo Saipuu throws some ecchi perversion into the mix as well, something that Recorder to Randoseru doesn't dabble in.
When Mifune fell hands first into Chiharu's bulbous, bulging bosoms one day, he had no idea his life would change forever. For the girl is a member of Eiken, a school club filled with busty beauties such as banana-loving Kirika and the exceptionally top-heavy child Komoe, and they've decided to recruit the boy as one of their own! With perverted situations at every turn, Mifune finds himself in frequent compromising positions, whether the group is participating in swimsuit bungee jumping, riding a yogurt slide in pairs or even seductively eating phallic food.
Boobs. Boobs to Cyclops is nearly what boobs are to Eiken, which holds a pair of extra large crowns. Both have the main guy getting into compromising situations with buxom females and fanservice ontop of fanservice, it becomes apparent after the first three minutes that either one would be low on plot and high on mammaries. No depth for either one, just come for the fanservice and leave logic at home.
What do you get with Maken-Ki? More boobs and more fanservice, which are already the driving forces of Cyclops Shoujo Saipuu. And some action, with fanservice. The mammaries are larger, it's not based on incest and in Maken-Ki, the guy is a harem protagonist, meaning he gets the crap beaten out of him for being a perv instead of Cyclop's girl on boy action. But, you know, jugs. The reason to watch either one.
Takurou Mikoujima is an avid fisherman who loves nothing more than to sit alone on the pier and cast his line, enjoying the peace and relaxation that follows. But the boy’s pleasant, angling days soon come to an end when he gets an unexpected catch: a fat-tailed mermaid named Muromi whose very presence is anything but soothing! She’s nosy, rash and prone to violent outbursts; and what’s worse, she has friends! Whether the boy is harassed by the forgetful Harpy, the cheerful dolphin-lover Hii-can, the busty Fuji or the rest of Muromi’s wacky companions, one thing’s for sure: Takurou’s quiet days at the beach have come to an end!
Both series have large amounts of fanservice and no real overarching plot to them. Both series are short, Saipuu however is a great deal shorter than Muromi-san in terms of episode lenght and uses fewer rehashed tropes and clichés but still provides some fanservice along it's way.