Translation of "Delusion" in Japanese

That girl is under the delusion that she is a princess.

あの少女は自分が王女様だという妄想にとらわれている。

When I was a kid, I thought that if I died the world would just disappear. What a childish delusion! I just couldn't accept that the world could continue to exist without me.

小さいころは、自分が死ねば世界は消えると思っていた。幼稚な妄想！自分はいないのに世界が続くのは許せなかった。