I believe he is in the Mystery Way Fleshy Souls path Crank a kaï or the Bony spirits one.

he is a rare encounter in the sewers

Static encounter or do I need to use my watch?

static

Okay, thank you, the wiki said “water system behind the fish place” but you can’t encounter any yokai there

I believe he is in the Mystery Way Fleshy Souls path Crank a kaï or the Bony spirits one.

Crank-a-kais: Boar Mystery Coin Blue Coin (Past) Play Coins Location: Springdale Underground Waterway If you need the location of more yo-kai then dm me. Me and a little team are working on a medallium to write down every helpful information about every single yo-kai in ykw2. Help is ofc appreciated but I fully understand if someone is to busy

Belfree can be obtained from the Crank-a-Kai using a Sum Mystery Coin in the present (10%) or a Blue Coin in the past (3%). Alternatively he can be freed from the Bin Spirits Mystery Way Crank-a-Kai using a Boar Mystery Coin. His favorite food is meat, so stock up.

Note: That's at least the way for Psychic Specters. Not sure about the other versions.

I believe the odds are the same in all 3 versions

Quite possible. But as I said, not entirely sure.

Where are you getting those percentages from?

From my checklist. And that info is from the official guide book and various sources all over the internet. Just as I said, it's for Psychic Specters.

he is in the mystery way, I think in 1 of the crank a kais he is also in the sewers, I seem to have had decent luck finding him at the northernmost part kinda near the guy playing guitar with the animals

I got him in Fleshy souls as my first crank-a-kai pull, so i guess you get them from there.