Dimension Fusion: From the Start, I Become a Reincarnator

Hu Lai is reborn, or perhaps he transmigrated. He thought he could live a simple, carefree life as a copywriter, waking up every day in a bed spanning more than fifty thousand square meters and facing over two hundred beautiful maids. But then...

On the news, he sees Kamen Rider with dubbed sound effects like “What just happened?” and “That energy bottle guy is crazy awesome”; Xiao Yan, who can turn battle qi into a horse; students at school practicing the Breathing Style; and a Devil Fruit user who ate the Gold-Gold Fruit, a “billionaire” in every sense of the word... Hu Lai had planned to lie flat after realizing he couldn't become a copywriter, but unexpectedly gained the unique status of a reincarnator. And so began a life of saving countless dimensions when busy and showing off in the real world when free.

Worlds visited so far: Sword Art Online (completed), Demon Slayer (in progress)

P.S. The protagonist's power system is based on Rimuru from That Time I Got Reincarnated as a Slime. He turns into a slime at the end of the first world.