We already know that Monster Hunter Portable 3rd has multiplayer baths. Or, to put it another way, the bathhouse in Yukumo Village acts as the game’s meet-up spot for hunters.
Here’s a very neat fact, though: it seems like you don’t necessarily need to be in ad-hoc mode to meet with other hunters that you’ve previously befriended — you can do it in single player mode while playing entirely by yourself, too.
This works through Portable 3rd’s Guild Card system. Think of the Guild Card as your personal ID. It keeps a record of your hunts as well as a customizable profile with a picture. You can exchange these Guild Cards with other hunters to befriend them.
Once you’ve exchanged Guild Cards, the other hunter — whose data will now be stored locally on your PSP — will randomly pay visits to you at the Yukumo bathhouse, bearing gifts or upgrading your bath’s water.