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?
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.
Fuuka may have the voluptuous body of a well-endowed twenty-year-old girl, but in reality she’s only a fifth grade student. After her mother goes overseas to work, Fuuka moves in with her relatives – including the masturbation-obsessed, eighteen-year-old Jiro – and begins attending Tonbori Private Elementary School. Between meeting new friends such as Miki and Kenji, Fuuka finds herself learning about lingerie clubs, the best way to put on a swimsuit, and when it’s not a good idea to walk around the house naked. For a typical elementary school student, Fuuka’s not-so-typical body helps keep every day a new adventure!