Since there aren’t many Legendary Pokémon in Generation 7, we could expand the roster to also include the Ultra Beasts, as well as Type: 0 and Silvally.
Viewing post in The Legendary Pokemon Breeder comments
Actually, he’s always considered all of them. The ultra beast will be in their own chapter. I don’t know the full story because he hasn’t made it yet, but it will be the MC finding them fucking them and sending them back to their world. And I already gave him my idea for Silvally along while ago, but he seems to enjoy maybe doing
Type: Null and Silvally are already counted as Legends so they were already going in.
The Ultras will get a side chapter where the MC goes into Ultra Wormholes to find and fuck them, he won't capture them since they technically belong in other worlds and not his... I'll think of some excuse for why he catches Necrozma though
I feel like it's fairly easy to justify catching Necrozma.
1. She is likely to be one of a kind, unlike other beasts
2. She is ecologically important as the source of light for Z-Moves and Ultra Space as a whole
3. She is in the black crystal form because she was injured and contained/imprisoned by the ancient form of the Ultra Recon Squad. A while ago it was suggested that that something about how the MC fuckee Solgaleo and Lunala allowed him to alleviate that pain.