This is a very immature joke a friend and I came up with. To get it you'll have to know how the kappa gets hold of the soul (or shirikodama). If you don't know, look up the kappa folklore.
Nini the Cute Kappa is a character I came up with not so long ago. If you type in "kappa" here on DA you'll see a ton of cute little thingies which is pretty funny when you think about what Kappas are like according to Japanese folklore. So Nini is a joke on that. She has the modern cute look, yet the not so cute...interests of her ancestors.