お世話になる

You usually pair it with the particle に to show who is helping you. For example, 田中さんにお世話になる means 'to be helped by Mr. Tanaka.' If the help already happened, you use the past tense: お世話になりました. In a business setting, you’ll hear the continuous form お世話になっております constantly. It’s the standard 'hello' in emails.

Use this when you start a new job or move into a new apartment to greet your neighbors. It’s perfect for thanking a host after a homestay. You can also use it when a doctor treats you or a teacher mentors you. It’s the ultimate way to show you don't take their effort for granted. Even if you just spent a weekend at a friend's place, this phrase is your best friend.

Don't use this for tiny, one-second favors. If someone drops their pen and you pick it up, they won't say お世話になりました. That would be way too dramatic! Just a simple ありがとう (thanks) works there. Also, avoid using it with people 'below' you in a hierarchy in a way that sounds patronizing. It’s a humble phrase, so keep it focused on your gratitude.

Japan is a culture built on 'Giri' (social obligation). When someone does something for you, it creates a small bond. お世話になる acknowledges that bond. It shows you are aware that you aren't succeeding all by yourself. It’s a way to keep social gears grinding smoothly. It’s so common that business people often say it out of habit, even to people they’ve never met!

The most common version is お世話になりました (I was in your care). In business, いつもお世話になっております is the gold standard for 'Thank you for your continued support.' If you want to be super casual with a close friend who helped you move, you might just say お世話になったね！ with a big smile.