Yeah, that's part of what I don't like is that she just leaves, even if that makes sense too. She wants to see the world that she loves that has Mari in it which she loves... but not with Mari? Even if she no longer has the love she felt as a mermaid, which is supposed to be way more powerful than a human's love, and that contrast makes her feel dead inside (like coming down from a strong high), why not be with Mari, who loves you? It's pretty selfish (heh), honestly. Granted, she's been selfish (hoho) from the start, but still.

But that's okay. Mari can just hang out with me instead.