GARMIN:
I am Japanese so I may give some tips for you.
You should know these words.it’s included slangs.
“肥育” (hi iku) : feeding something.
“自己肥育”(zi ko hi iku) : feeding myself.
“強制肥育” ( kyo sei hi iku) : force feeding.
“肥満”( hi man ): obesity.
“肥満化”( hi man ka) : Get fat. This word is not popular. It is used only in community.
“太る”(futo ru) “太った”( futo tta) : get / got some weight. It is popular phrase.
“デブ” (de bu) : fatty. This is a dirty word. Don’t use it without trusted gainer.
“デブ専” (de bu sen): Someone who loves only fatty man/woman.
“ぽっちゃり”(potchari) ぽちゃ(pocha) : plump.
“みけぽ”(mi ke po) : more than 100kg(220lbs) size.

“肉塊”( niku kai): It means meat block. But in the community, it means immobile obese ( Almost use on fantasy fiction).

As far as I know, Japanese feeder / gainer community like fantasy feeder is not exist. Almost Japanese gainer / feeder use Twitter. So search Twitter and use mentioned words.

Let me know If you need another information.

Eating Dude:
Hi,

I always think about feederism the last few days and also chat with people about it. To be honest it makes me horny and I can't focus very good on tasks I have to do!

How do you manage this??

Miachu:
I ended up ghosting all my friends for like 2 days, I honestly felt so down and embarrassed over it, and what made it worse is my BF say it

However I've spoke to some of my friends about it now

Spike:
I do not wear pants as they never stay up or my belly makes it look like an intertube. I havent looked back since 2011 when i stopped wearing leg prisons.
Fuck them pants XD

Slasher92:
Arguably one of my favorite forms of sexual intimacy. It’s also really fun to tease said partner that they’re fat enough that their belly is now another hole to fuck.

Previously I’ve had past partners sit on a toy while having their belly fucked. Makes for a very fun experience 😇