[justsomeguy]

Originally Posted by AC-Phoenix

Locked room purpose:
Creating the illusion of a witch... Ohw ait wrong anime - no seriously its ujust the culprits modus operandi in order to not cast suspicion upon her as there is only one prson able to enter without being noticed - Konousu

"In order to not cast suspicion upon her," Kounosu creates a situation where only she can enter the room. That's counterproductive.

No other ways to enter and the unused rope

There's a massive problem with your theory regarding the laundry chute/dumbwaiter or whatever that thing is. Kounosu still cannot exit without a high chance of Kaitou noticing, and naturally being even more suspicious than if she had just walked in the door like any normal person would.

Big boy vs small girl:
If my theory is true he was probably pretty surprised wheen she emerged from there - and even then trusted her, it is clear that the culprit is someone the victim trusted so even a small girl like kounosu could have killed him

It's pretty hard to trust somebody when they've just crawled through a hole and they're approaching you with a weapon (and she needs one, otherwise she has no chance). To incapacitate Kaitou as quickly as possible to prevent noise and struggling, a knife would not work unless applied to the neck or stabbed through the skull. There was no such injury to the body. Kounosu cannot possibly successfully strangle Kaitou, either. Therefore, she must have had some sort of blunt object to KO him with a strike to the back of the skull, which means she's carrying at least two weapons. Even if we discount the arm and the huge amount of blood, based on what we've seen of her script Hongou would have specified an alternate fatal wound to take into account.