They're certainly a rather interesting character. Both for the audience and, in a different way, presumably for the people in their life (Noelle and Toriel in particular).
They’re mischievous, mysterious and an introvert… Like me! They are very, very interesting and we will probably find out more about them in the next chapters!
hmm... seems like a nice kid (although a prankster) then there's being controlled part and there's also what happens at the chapter end - I feel it's too early to judge