it just idea

Adams third child, Seth: What is that?

Seth:

He's been odd since his first visit to another universe, and Mobei Jun is eventually able to piece together that he met himself there... And that the alternate version of himself had only one wife and felt no need for more.

As soon as he heard that Mobei Jun knew this would be a Problem. Women are Junshang's only vices, and it doesn't take a genius to guess he's looking for something in them that he cannot find within himself. That such a woman apparently exists, but only in another universe must rankle him.

And indeed Junshang abandons his usual bride collecting habits, and turns to trying to find this mystery woman in this universe or others.

The travelling between universes worries him, his people have many such stories about that type of travel going horribly wrong ... He's almost relieved when Junshang returns from one of these trips with a strange flat blue box trailing him. Maybe it will inspire Junshang to stay home more often. (Mobei Jun is a little sick of taking on all of these disasters Junshang usually handles.)

And Junshang does stay, his attention split now between his duties and whatever strange projects the box tells him.

The collapse of the harem is inevitable. Most of the women leave with their divorces and a chunk of the Treasury without complaints. Some make things difficult though... And a few, only three or so, stay anyway, presumably out of love for their husband. Though perhaps they just truly have nowhere else to go.

The machine Junshang pours most of his attention into is bizarre. Mobei Jun won't pretend to understand what it does. (He does have a generator installed in his own palace, electric lights are far less labor intensive than candles or magic lighting.)

The machine says a lot of things in the same tinkling voice the blue box used. He doesn't understand most of them, but eventually Junshang gets what he wants out of the machine it seems.

He leans over the large blue screen, eyes fixed on a blinking dot on it.

"There you are." Junshang says.

"WARNING! LOW PRECISION MATCH! CANNOT PERFORM EXACT RELOCATION!"

"We don't need that! Make the transfer!"

"WARNING! ESTIMATED SIZE OF TRANSFER -"

"I don't care! Do it!"

There's an enormous earthquake then, Mobei Jun has to kneel to avoid falling over, it's brief though, over in a few seconds.

"What did you do?" Mobei Jun asked.

"I found him," Junshang said. "And brought him here."

Him? Huh.

The machine chimed again. "Relocation of City of Shanghai complete, approximate population transferred with greater metropolitan area 24,000,000."

Mobei Jun stared. Junshang stared.

"How many?" Junshang said.

"Target Shen Yuan resides in Shanghai Municipality, due to low precision seeking Target's entire hometown was relocated to ensure his safe transfer. Estimated population of Shanghai is 24 million people."

Fictional small town in the middle of nowhere in real country: par for the course in any genre

Fictional major city in real country: standard fair, but it's usually clearly based on a real city

Fictional suburb of real major city in real country: strange but I can see the application