Many chapters ago I said Kokoro is quite similar to Rai. Now you can add to the list falling for a person because the person has already fallen for someone else, and only that made them stand out. It'd be cheap writing to throw Kokoro into the drama, though. I hope she's mature enough not to do anything about it, despite appearing now. If she just entertains the feeling for this single time and then suppresses it, it's fine. However, if she turns into a female Rai for real, I doubt I can keep reading this series. One Rai is already nearly insufferable.