Why Japanese people keep giving you food you didn't ask for
A colleague of your host presses a small wrapped box into your hands at the door. A guesthouse owner leaves regional sweets on your bed. Someone from a tour group you barely talked to hands you something from their bag before getting off the train. You accept it, say thank you, and have no idea what just happened.
Omiyage. Bringing back regional souvenirs, almost always food, for people at home or at work after a trip. It's taken more seriously than you'd guess. Someone back from a weekend in Kyoto will usually bring individually wrapped sweets for the whole office. Not most of the team, everyone, and the count gets worked out before they even buy the box.
The gift matters less than the fact that they thought of you while they were gone. Price barely enters into it. What matters is that it came from somewhere specific, somewhere they actually stood. Buy something in Tokyo and pass it off as a Hokkaido souvenir and you've missed the point entirely.
If you're staying with a host family or being shown around by a local contact, showing up empty handed gets noticed. Nobody will say anything about it. But a small food gift, from a specialty shop or from home, tells people you understand how this works.
Skip the speech when you hand it over. Gift giving here is understated to the point of looking reluctant, the giver downplaying it while the receiver accepts it. "It's nothing special, really" is close to a script. Most people won't open it in front of you either, though that's loosened up some. If you're unsure, wait to be told you can open it.
The wrapping is worth a second. Japanese gift packaging gets absurdly careful, folded paper, a ribbon somebody clearly thought about. Tearing through it while they watch doesn't land well.
Temiyage is the same idea for visiting someone's home. Bring something, keep quiet about it, let the gift do the work. Alcohol, fruit, sweets. Skip anything too practical, it reads as transactional.
You don't need to study this. Most people here are generous with visitors who are obviously trying, and getting close is enough. It's not about the item. It's about someone remembering you while they were somewhere else.
So if a stranger hands you food at a train station and you're not sure why, just take it. Nothing's happening that you're missing. Someone's just being kind, and they don't want anything back for it.