Board Thread:Questions and Answers/@comment-30745677-20161213225627/@comment-27701762-20161214045755

Soooo...technically you should be playing the game first before asking this question. Since the answer to that is a pretty integral part of the story.

If you're really impatient and just want the question answered immediately, you can visit and read the respective pages for Frisk and Chara. But I would highly recommend that you refrain from doing so until you've had a chance to discover it for yourself.