Simple Domain Swordsman chick also didn't wanna go along with killing him. Hell, she's probably the nicest person in the series overall.
I know people are going to die. Author is doing a great job making you like these people, and then boom, punches you in the chest like Kakyoin. Its hard to do, but its what makes a story great in telling when you know people are going to die but the author has the guts to do it.
Almost every Jujutsu sorcerer in some fashion has some likeable qualities, so when one dies it makes it hard to watch. Which is why the 2nd Ending is such a big death flag because the ED Video is all about, "Make sure you record each memory, because with the job, you never know when your friends will die. Treasure each day."
It also brings back to Yuji, he is supposed to die in the end because that's the deal when they get all 20 Fingers. But now, as he makes his slow walk to death, he has to watch all of his new friends die before him.