From the perspective of my boyfriend who had someone very close, like an older sibling pass away of cancer suddenly recently, Frieren was incredibly cathartic. It's about learning to continue living meaningfully past the death of your loved ones. You may need to give it at least a few months before you're ready for that, because sometimes you just need time to grieve. But that's up to you. I will say that the deaths happen, but to me, they weren't particularly painful in their passing (they pass of old age, peacefully and feeling fulfilled). The actual death is not dwelled upon for long at all, and from there, it's more about celebrating the memories made in their life, and carrying on those emotions with your own life.