Learn Hardcore Japanese: watasi ha asita hikkosi wo simasu.

は is the topic-marker. It tells the listener “as for me …,” focusing on the whole sentence about “me.” By contrast, が is a subject-marker that often introduces new information or emphasizes the subject itself. In this case, you’re simply stating what you (the topic) will do tomorrow, so は is natural.

What’s the role of を after 引っ越し?

Here 引っ越し is a noun meaning “moving house,” and を marks it as the direct object of the verb します (“to do”). The structure [NOUN] + を + する turns many nouns into verbs: 引っ越しをする = “to do a move,” i.e. “to move.”

What’s the difference between 引っ越しをする and 引っ越す?

Both mean “to move (house),” but:

引っ越す is a single verb.
引っ越しをする is a compound of the noun 引っ越し
- する.
  They’re interchangeable in most contexts; the する-form can sound a bit more formal or emphasize the action as an event.

Why doesn’t 明日 take a particle like に?

Time expressions often act as adverbs in Japanese. When they appear before the verb, you can drop に. So 明日引っ越しをします naturally means “Tomorrow, I will move.” You could say 明日に in very formal writing, but it’s rare in everyday speech.

Why is the verb します at the very end of the sentence?

Japanese follows a subject-object-verb (SOV) order. Particles mark each element’s role, so the verb always comes last. You know 私 is the topic, 引っ越し is the object, and します completes the thought.

How do we know that します means “will move” (future) and not “move” (present)?

Japanese doesn’t distinguish present vs. future in its verb forms. します can mean “do/does” or “will do.” You rely on time words like 明日 (“tomorrow”) to signal that it’s referring to the future.

Can we omit 私 in this sentence?

Yes. Japanese often drops pronouns when the subject is clear from context. 明日引っ越しをします still means “I’m moving tomorrow” if it’s understood who you’re talking about.

Why is there a small っ in 引っ越し?

The small っ indicates a doubled (geminate) consonant in the following syllable, giving ひっこし (“hikko-shi”). The underlying verb is 引っ越す (ひっこす, hikkosu). When you form the noun 引っ越し, you keep the small っ to reflect that pronunciation.

Is 引っ越し technically a noun or a verb here?

By itself, 引っ越し is a noun (“a move”). When you add を + する, you create a verb phrase. So in 引っ越しをします, 引っ越し remains a noun and します is the verb that carries tense and politeness.