I Want To (たい)

たい conjugates like an い-adjective from here on: 食べたい becomes 食べたくない (don’t want to), 食べたかった (wanted to), 食べたくなかった (didn’t want to). None of that borrows from 食べる’s own conjugation pattern, たい runs on its own rules once it’s attached.

たい is only for your own wants, stated directly, the same restriction Korean’s 고 싶다 has. Talking about someone else’s want needs a different shape entirely, たがっている, not just swapping the subject into a たい sentence.