Mizutamatchi can go into a Kuchi teen. I don't think that it necessarilly needs to have high kindness points. I think it is more random than anything but to increase your chances you should maybe try to get high kindness anyway and don't take perfect care of it. The kuchi family is hard to get because you won't get kuchi by taking bad care or really good care, it has to be somewheres in the middle. I hope this helps.