Quote Originally Posted by Buffalobiian View Post
The Biwa demon also stays in the castle, so if they got a Hashira in there and killed her then that's a huge asset lost to Muzan without much gain. Killing a Hashira or two doesn't mean much to him. .
THat's why he's bringing ALL the demon slayers there now, makes sense /s.

He could just teleported important assets to outside Japan. Just get Biwa to Europe where there's no Hashira.