For me mikasa is stuck at the first two training actions and no matter how many times I do them, they stay at 2 stars and I can't use the others. I've finished everyone else except her.
You can do others, just do it gradually. Ask her to turn around > show her tongue and so on. Then return to first two once you've completed the rest.
I thought the kiss was the next one in order because it's also 3 hearts but I'll try that
