I'm looking for a psychological oneshot that I read back then. I think I still remember the whole story?

Basically, this guy meets this girl that has this obsession with death. The girl has this theory that the bigger the creature the harder it becomes to kill it. She made this sort of hierarchy, insects being the easiest then rabbits(or whatever), then, at the top, the hardest to kill, humans. So, she tested it out, eventually reaching the level of having to kill a dog. In the end, she couldn't kill the dog and ends having some kind of breakdown. The guy comforts her. The girl then murders the guy, realizing that humans were easier to kill and therefore were a level lower than dogs in the hierarchy. That's basically it! I hope you guys can help me out!

I think it is Nani Made Nara Koroseru? from Oogiri.

~4400 manga completed
~1700 ongoing...

IT IS INDEED! Thank you!!! 😃