Credit to https://www.ign.com/wikis/dragon-quest-xi/Puff_Puff_Sessions
There are 8 opportunities in the game for our Hero to relax and get a... uhhh, massage
None of these are missable and can be done at any point in the game
Puff Puff いち - - Hotto
This Bunnygirl is found at the balcony in the back of the steam baths and asks to be paid 20 gold coins for a session.
Puff Puff に - - Gallopolis
You'll find this Bunnygirl standing outside the armor shop and is probably the shadiest of all the puff puffs.
Puff Puff さん - - Gondolia
This Bunnygirl is waiting at the circular pathway off to the northeast section of the city.
Puff Puff よん - - Upper Octagonia (Battle Arena)
This one is in the southeast corner of the area before the place gets transformed into a casino.
If you miss her the first time, you'll get another chance for a session when
Puff Puff ご - - Upper Octagonia (Casino VIP Area)
This Bunnygirl is not far from the entrance after you defeat Booga and the casino is back under human management.
Puff Puff ろく - - Phnom Nohn
You'll find this Bunnygirl at the second floor of the inn, by the small balcony across from the beds.
Puff Puff なな - - Sniflheim
This Bunnygirl is hidden in the corner next to the front desk of the inn. Talk to her and she says to meet her at the harbor bell during lunchtime. Rest at the inn until noon and head for the docks. The bell is just to the right as soon as you step out of the town proper.
Puff Puff はち - - The Battleground
Our last Bunnygirl is standing on the path in B9. You should have no problem finding her, as she is not all hidden. Follow her outside for a really intense puff puff session.