It was really dark! And to think this was a Digimon game! A DIGIMON game! At one point - I won't say who in case you'd like to play it - but during my first playthrough, one of them dark digivolved and ate his partner! Blood spattered across the scene. It was very reminiscent of an Attack On Titan death. What made it even darker was the Digimon crying out in pain that its throat hurt. Obviously, the "true ending" is much more light-hearted because no one dies, but depending on the timeline you're on, it can be downright bleak!
It isn't that much of a pain to get everyone to survive once you get a good grasp on the game mechanics, but I had no idea what I was doing the first time around. For example, I didn't know that a character's affinity could increase their chance of survival at first. I just thought it increased their chances of supporting you in battle, so I wasn't as adamant about the player character bonding with them. :-D
