It sounded like trash brilliance. In this show, a battle power-up means getting your tits out for a boy to suck on. Boob size might also be related to power level. In ep.2, huge boobs trump smaller ones.
Unfortunately, though, I'd underestimated the show's depths. Katja... no, goodbye. Not watching this. I'm off. It has a character (Hana Katsuragi) who can't resist her lust for an extremely underage evil dominatrix.
The male protagonist is Sasha, a thirteen-year-old Russian who'd have grown up if he became a brat. He thinks social skills are for wimps. He's also the one who does all that breast-sucking, which lets him defeat baddies. (This show is extremely violent, with gore and killing. One villain self-immolates.) He's rude to the class alpha bitches and he has a background of torture experiments.
The girls who mysteriously endure him include Mafuyu (main heroine) and Tomo (best friend with big boobs and negligible brains).
Even if we ignore the offensive material, the show isn't great. It'll have silly scenes of boobs, shopping for bras, etc. Then, in addition, it has non-consensual boob-sucking for combat reasons. Eww. This show is crass and exploitative. That's the point. Obviously. But it's also questionable in ways that have Western anime fans deleting online references to it, arguing that some shows don't even deserve to be catalogued.