There is a bubble bath bottle at Meowy's Mporium in the exchange bin. First, you should take the hypnotizing kit.
This is the low-spoiler guide for "Getting the bubble bath bottle" 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.