Learn Hardcore Japanese: watasi ha syuumatu ni yakyuutaikai ni ikimasu. - I will go to a baseball tournament on the weekend.

In this sentence, は marks 私 (“I”) as the topic of conversation—what we’re talking about—rather than introducing new information. が is used to mark the grammatical subject when you’re presenting something new or emphasizing it. Since you’re simply stating what “I” do, は is the natural choice.

Why are there two に particles—one after 週末 and one after 野球大会?

Japanese uses に for different roles:

After 週末 (週末に) it indicates the time when something happens (“on the weekend”).
After 野球大会 (野球大会に) it marks the direction or destination (“to the baseball tournament”).
Although it’s the same particle, context (time vs. direction) tells you which function it’s serving.

Could I drop 私 here and just say 週末に野球大会に行きます?

Yes. In Japanese, the subject or topic is often omitted if it’s clear from context. Without 私, you still clearly mean “I’m going to the baseball tournament on the weekend,” as long as your listener knows who you’re talking about.

Why is it 週末に and not just 週末?

To specify when you’re going, Japanese needs the time‐marking particle に. Without に, 週末 by itself is just a noun (“weekend”) and doesn’t convey “on the weekend.” You could say 週末 in casual speech and have someone understand, but grammatically 週末に is correct for “on the weekend.”

What’s the difference between 野球大会 and 野球試合?

野球試合 (しあい) means a single baseball game or match.
野球大会 (たいかい) refers to a tournament or series of games, often with multiple teams competing.
Here you’re attending a larger event (大会), not just one standalone game.

Can I use へ instead of the second に for the destination?

Yes. 野球大会に行きます and 野球大会へ行きます both mean “I’m going to the baseball tournament.”

に emphasizes the goal or arrival point.
へ highlights the direction toward that place.
They’re largely interchangeable for simple motion verbs like 行く.

Why is the verb 行きます in the polite form?

Japanese verbs have plain (dictionary) form 行く and polite form 行きます.

行きます is used in formal or polite contexts (e.g., talking to strangers, superiors, or in writing).
行く is more casual, used with friends or family.
Here you’re using the polite form, but the meaning (“to go”) is the same.

Is the word order important? Could I say 野球大会に週末に私行きます?

Japanese word order is more flexible than English, but natural sentences typically follow Topic–Time–Place–Verb:

私は (topic)
週末に (time)
野球大会に (place/destination)
行きます (verb)
Shuffling them too much can sound awkward or confusing. Your original order is the standard and clearest way to express this idea.