Anyone been to a KUDOCHI private onsen? Need advice!

Me and my Boyfriend were trying book a private onsen room the day we land into Tokyo (11th May) but when trying to use the website to book it, it says no services available? Are we trying to book it too early in advance or is there no spaces left? The website feels very confusing. It has to be a private onsen as I have tattoos :")

Any advice would be appreciated!