Stories Of Another World

Tazumi Riku gets displaced into another world, and goes on your atypical isekai adventure; successfully slaying both the Demon King and his Lords, collecting a dizzying amount of heroines, and creating his own empire/alliance from scratch. That was two hundred years ago. The First Hero may be dead, but his descendants live on, blessed with extraordinary powers and Unique Talents that would aid them in their saga. But not all is well in paradise; a demonic plot blankets the break-away states of the empire, and the polities that had once been united through common cause now find themselves hoarding conflicting interests. It is up to the Virtual Hero, Ex Albio, and his party to once again tame the rise of the second Demon King.

However, on Earth, a mysterious structure appears in the middle of Ginza street...

You can use this universe and add some other Vtuber companies except Nijisanji. I already have the Nijisanji part covered. [Lots of OOC]

Also, before I forget, I am talking about real people here, so when you get into the rabbit hole, restrain yourself and show some respect. Though they have the mask of anime girls and boys, they're still people. People with boundaries that you should follow.)