Honestly I think both endings are pretty grim. Erx is not a good person, and I don't blame Yumi for leaving him to die, but he's pitiable, too.
The writing is good, to be clear! The gameplay is too. It gets a bit repetitive after the first few playthroughs, but that's pretty normal for jam games.
If there's one thing I have to say, it's that having to spend two turns to get the one energy you need to play a card makes things feel slow.
I kind of want to be able to see a full list of all the dialogue, to see if there's anything I missed.