"Has anything in your life ever felt strangely familiar?"
"How can you be sure that the reality you believe in isn't another dream dimension?"
"If I'm trapped in layer upon layer of dreams, where is the real me?"
"I thought that unraveling each dream would bring me back to reality, only to find everything had returned to the beginning. It was all a cycle of dreams."
(No harem, no formulaic tropes, no overpowered protagonist, no System, no brainless plot, and no wish-fulfillment. Please proceed with caution if any of these are deal-breakers.)