Modern fictional setting, a short story
It's a knife [although I think it's candy]
Amnesia fish warning, probably multiple memories to kill
It's a private birthday setting for Qiang Rabbit, and it's set as a close friend of all members of the Demon Slayer Corps. He probably treats Giyuu like a silly son who dislikes a landlord's family.
Probably a daily record of volunteers who try to live a normal life but always fail.
Concept: Knife