Anyone who has worked in Japan in some capacity knows that there are a lot of social functions outside of work that actually semi-count as work. Welcome parties, end of year parties, new year parties, farewell parties. They serve to confirm that you are part of the group, and the free-flowing booze loosens lips, allowing sensitive topics to be discussed in a relaxed atmosphere.

The one problem with these parties is that they are expensive. In the small town where I worked, they cost at least 3000 yen (roughly $30) but were usually 5000 yen ($50). You get a nice dinner and as much beer as you are comfortable with. I went with the junior high school, sometimes the elementary schools, the people at the apartment building where I lived, and the Board of Education. As you can imagine, the cost adds up, especially around the end of the calendar and academic year.

I rarely refused for financial reasons, but I know other teachers who did. I was sometimes unable to go due to scheduling conflicts, but I felt really bad when I couldn’t attend – the parties were fun, and I was in a small enough town (8000 people) that finding a way to socialize was difficult. During the farewell party for the junior high school in my third year, I noticed that the young computer tech guy was carrying a giant bottle of nihonshu. At some point he stood up and announced that the head tech guy, who was not present, had given it as a 差し入れ. That was when it clicked. He couldn’t make it to the party for whatever reason, so he left a present instead. If only I had known that throughout my time in the town.

差し入れ (さしいれ), which literally means “insert,” can be considered a kind of preemptive omiyage of sorts. Often it’s given when you can’t attend an event, and in those cases it’s usually liquor. It’s a fantastic custom! It shows that you really wanted to participate, it probably costs less than the meal, and your coworkers will gush over you once they’re nice and boozed up and finally make it to your bottle.

Nihonshu and shochu are both appropriate 差し入れ for parties, but I recommend shochu since it can be split between more drinks and watered down for people who don’t drink that much. It will also increase your 渋い factor.

差し入れ are appropriate in other situations, too. If you know someone is studying or working overtime, bring them some coffee. It looks like people also give it to contractors doing work on their house, in which case nikuman, warm oshibori, or coffee are all winners.

Everyone knows about omiyage, but I feel like 差し入れ are somewhat uncharted. Hugely useful. Win friends and influence people with this cool custom.