I still keep my believe of Mai having something, however she is 10, so she doesn't know how to call the felling she has on her chest. If you recall, when Tae suggested she was feeling jealous she didn't deny it, she was merely confused. Tae cut the topic as she thought that wasn't the case, but as we see it: that was the case, Mai is just too young to fully comprehend the concept.
It is still weird to support a 23 yo relationship with a 10yo, but personality wise, is not a bad development.