I don't know how a manga that started as an ecchi harem ended up with such a convoluted story. Ikeda just adds new family members when he gets stuck. Oh yea, this is her "other" sister and she is also a bitch. Even side characters get family members popping up to join canon. I miss the days when the moms came to school and tried to get their daughters to give their virginity to Tsukune. Now they are on an island in the sky or some shit. Everyone and their mother knows where they are. They send out enemies one at a time for no reason besides to look like some gladiator game. Moka is like cuddling with a giant thing straight out of Alien to like wake it up, while her yandere sis-con sister is being stupid. Then you even have immediate traitors, old school-mates showing up, and everyone showing off their lame shit after a training arc.
The only thing worse is the piece-wise bullshit that is Negima. And being stated to be similar to Negima is not a fucking compliment.