Without a System, I Build a Knockoff Main God and Travel Across the Heavens

After dying and transmigrating into the world of Hunter x Hunter, Xiao Ming discovered that he had no all-powerful System. Instead, he combined the mysterious energy in his mental space with Nen Ability and set about building his own way to travel between worlds as the Lord God.

Worlds featured so far: Hunter x Hunter, History's Strongest Disciple Kenichi, Kengan Ashura, The King of Fighters, Demon Slayer, JoJo's Bizarre Adventure, Claymore, Unbreakable Machine-Doll, Rozen Maiden, Mieruko-chan, Shaman King, Toriko, Akame ga Kill!, Strike the Blood, One-Punch Man, The Morose Mononokean, Campione!, Welcome to Demon School! Iruma-kun, High School DxD, Gabriel DropOut, Problem Children Are Coming from Another World, Aren't They?...

Before reading: This is a crossover harem story with an extremely slow pace and slow-burn development. Each world gets a very long arc, and it's an enormous mash-up.