Of course they would. They have full teams of lawyers that could tie him up with legal fee's for years until he gives up.
He's not in the same league as Nintendo financially or legally, don't talk wet.
Ya Nintendo would have raped him in court. Yes there are parody and fair use laws which can protect you to a certain degree when mimicking copyrighted content but in this case his downfall is the fact that the representation of the individual pokemon, which are Nintendo property, are too good to be anything but copyright infringement.
Here are some examples of pokemon based parodies that would win in court for comparison:
Con-Quest! Poke-con
Haremon
Oppaimon
For another example of a game that is riding the line or would also lose in court look at:
Pokemon Ecchi Version
There are plenty other examples of games on here that could get rumbled by DMCA C&D orders but fortunately most other companies tend to be more relaxed (read as less asshole-ish) than Nintendo as long as you're not stepping on any official product in the process or trying sell it.
Case in point
Something Unlimited. As I recall early in the project like 2 years ago the devs that became Gunsmoke Games got in trouble with WB/DC over the fact they felt the original name "Injustice Unlimited" was too close to the names of their official cartoon/comics "Justice League Unlimited" and/or Mortal Kombat DC clone series "Injustice". It didn't matter that the show had been cancelled for a decade+, the comics run ended almost as long ago, and that the games were entirely different types there was a chance people could confuse the them which WB/DC didn't like especially since they were promoting Injustice 2 around that time. On the flip side WB/DC gave fuck all that they were using the DC characters in the art style of JLU in a porn game because as long as Gunsmoke wasn't trying to actually sell the game (crowd sourcing development funds doesn't count a lot of the time) it wasn't worth wasting their lawyers time because it makes the fans happy and potentially hungry for new official content.
Nintendo on the other hand has repeatedly demonstrated they'll beat people to death over a nickle if they can actually get away with it.