Pokémon: I'm The Digimon Emperor

He had transmigrated into the Nasuverse, becoming a magus. Nathan had originally thought his life would be spent fighting in the Holy Grail War, maybe saving humanity along the way... that sort of thing. But then he had obtained a Dimensional Forum that connected different worlds. Kocho Shinobu: "Excuse me, is it really possible for humans and Demons to coexist peacefully?" Nathan: "Immortal Demons make excellent experimental materials. They're the best candidates for working in mines or in nuclear radiation zones. Isn't that harmonious enough?" Haibara Ai: "I work in an evil organization. They killed my sister. How can I get revenge?" Nathan: "Take that drug that turns people into children. I'll annihilate all of them right away." ... Members from different worlds kept appearing in the forum. While helping them solve their problems, Nathan also picked up some local specialties along the way—and earned himself a few points as well.

After being reincarnated into the Fairy Tail World, Luca Blight obtained the [Strongest Puppet System], allowing him to acquire powerful puppets from other worlds. From the RE:Zero World, the appearance of the Sin Archbishops. From the Bleach World, the opposition and bloodshed between Soul Society and Hueco Mundo. From the One Piece World, the arrival of the Four Emperors, the Seven Warlords of the Sea, the Marines, and the World Government. And even Blue-Eyes White Dragon and Blue-Eyes Ultimate Dragon from Yu-Gi-Oh!, the strongest lineup of the ancient Egyptian Gods. All in all, before they knew it, one 'shadowy mastermind faction' after another had begun emerging within the Fairy Tail World. Only then did the big shots of the Fairy Tail World think they had finally come to understand the truth of the world. The Magic Council: "Are you saying that history is not as we have seen it?" The Black Wizard Zeref: "A Witch who can destroy the world? I wonder if she can kill me?" Acnologia: "..."

Jay Grayson, known as Brother Tiger, was once a Yangko dancer in Shanghai's underworld, a hunter disguised as a centenarian blond vampire, the youngest of the Ten Wizard Saints after Jellal, and so on. Voldemort dared not call him by name, legends of Brother Tiger circulated in the Caribbean, and the World Government listed him as its 'Biggest and Most Dangerous' wanted criminal. The Shadow Legion awaited his summons in the shadows, and the Otsutsuki Clan was forced to flee across the starry sky because of him. Every newborn soul in Hueco Mundo and Seireitei feared his name… and all of this began when he fell ill and was bedridden. Doraemon, who should have existed only in imagination, was accidentally destroyed in a time-space accident and became Jay's [Stand]. With all the magical gadgets lost, an illegally manufactured Dream Pillow became their only chance to retrieve them… First World: Kung Fu Hustle