watashi wa kafe ni techou o wasurete shimaimashita.

I left my planner at the café.

Breakdown of watashi wa kafe ni techou o wasurete shimaimashita.

• は: topic particle
• 私わたし: I
• を: direct object particle
• に: location particle

Questions & Answers about watashi wa kafe ni techou o wasurete shimaimashita.

Why is は used after 私?

は marks 私 as the topic of the sentence.

So 私は means something like:

• As for me, ...
• I ...

In English, we usually just say I, but in Japanese, は often introduces what the sentence is about.

So:

• 私はカフェに手帳を忘れてしまいました。 = As for me, I left my planner at the cafe.

Using が instead would change the nuance. は is the most natural choice here if you're simply talking about what happened to you.

Can 私 be omitted?

Yes, very often.

Japanese frequently leaves out subjects when they are already clear from context. In real conversation, people would often just say:

• カフェに手帳を忘れてしまいました。

This still naturally means I left my planner at the cafe, as long as the context makes it clear who is talking.

Including 私 can make the sentence:

• clearer,
• a little more explicit,
• or slightly more formal/textbook-like.

Why is カフェ followed by に and not で?