御中: belly, tummy, stomach, abdomen; a meal, especially of rice; cotton batting; (historical) the title of a maid working in the inner part of a samurai family's house during the Muromachi period

middle / in

middle / inside / in

Kyūjitai form of 悪夢 (“nightmare”)

(rare) a female given name

to have a dream

daydream

trance, dreamy state of mind

(idiomatic) sweet dreams!

Revealing that the entirety of a fictional story was all part of a dream the protagonist had; the "it was all a dream" ending.