Kappa stong? Well, he is attacking something made from paper, which is weak to water. If the opponent were made from stone, then he would not be as effective.
@Hounder
Who knows? High pressure water jets can cut stone. At the very least I imagine the streams he's slicing through paper dolls with might be able to injure someone.
She's every bit as bad at attending to what people actually say and at reasoning from it as some of the clowns on MangaDex, and on the 'Net more generally.