I dont think its the local (city) tax, as I've checked the Ibis Shinjuku & Pullman Tamachi both show free / no amount payable until the end of booking page as well.
Well unless its a "very" local tax as in Ginza's area tax.
I did check the details and all 3 hotels show the same note about local tax payable at hotel during check in time.
Also another thing I noticed was that it shows different extra amount if I put 1 adult / 2 adults / 2 adults and 1 child.
Anyway, I will check on check in later and update here for everyone.