The sanctuary of Duke

After a deadly incident, volo decides to take a step back from his path in life to open: The sanctuary of Duke. A momentum for his deceased teammate and friend. A sanctuary that holds once abused Pokémon along with the rare delta variants. Delta being, a Pokémon who's learned move set doesn't match the type it's born with. Everything is going smoothly until he agrees to an arranged marriage to help get his sister, Cynthia, out of it. It didn't matter much to him until a certain train loving, battle enthusiast takes up the other end of the deal in exchange to expand the battle subway into sinnoh soil. Can the two put aside their differences to help keep the sanctuary's Pokémon safe from a mysterious threat? Or will the marriage dissolve before it even began.