Shadow Pokemon are a bit like the Nuclear types in Uranium (but less shitty) where it's best to use a monotype pokemon against them because when they're supereffective against (mostly) all types, dual types take 4x damage.
Goodbye sweet Barb, you will be missed. you and all of your potential simple+calm mind sweeps.
from memory you should be mostly BS free til around gym 4? just battles though, A certain character is gonna to get real annoying plot-wise. and no it's not Crescent, she's always annoying because she obviously knows a lot about whats going on BUT NEVER TELLS ME ANYTHING.
Praise the Jesuscat, destroyer of bullshit, abuser of fields, slayer of spoons.
(suggestion that you may or may not want to implement: when replying to messages, have their messages displayed too.)
Rejuv is really good so I would still give it a shot. interesting to make the comparison to Garchomp as Mewtwo is much more beatable, and even if you do beat garchomp, you just get slightly different dialogue and then things continue on exactly the same and it doesn't matter at all. With Mewtwo it's not even really implied that you lost, It seemed to me much more like you beat it back enough to disengage from the fight and get past it, but it was able to regenerate itself partially due to the fact that it was overflowing with shadow power. (and Mewtwo can learn recover)