Cosmo is at Meowy's Mporium. I think he has a lot of information about Montameeuws.
This is the low-spoiler guide for "Dealing with Cosmo" puzzle in Nine Noir Lives. Unlike in normal walkthrough, you get gradual hints on how to solve the puzzle. Click the big button below to see your first hint. If the hint contains a spoiler, you will be warned about it before clicking.