sono simai ha syuumatu ni kouen de issyo ni sanposimasu

は marks その姉妹 as the topic of the sentence.

So その姉妹は means something like as for those sisters...

It does not directly mark the grammatical subject in the same way English does. Instead, it tells the listener what the sentence is about.

In this sentence:

• その姉妹は = as for those sisters
• the rest of the sentence tells what they do

A learner may expect が, but は is very common when introducing or talking about a known topic.

その means that and is used before a noun.

So:

• その姉妹 = those sisters / that pair of sisters

It usually refers to something already known in the conversation or something closer to the listener than to the speaker.

Compare:

• この姉妹 = these sisters
• その姉妹 = those sisters
• あの姉妹 = those sisters over there / those sisters we both know

姉妹 means sisters, usually two or more female siblings.

Japanese nouns usually do not change form for singular vs. plural the way English nouns do. In this case, though, 姉妹 itself already refers to a sister relationship, so it naturally means sisters rather than just one sister.

So その姉妹 is understood as those sisters or that pair/group of sisters.

Here, に marks the time when something happens.

So:

• 週末に = on the weekend / at the weekend

This is a common use of に with time expressions.

That said, with some time words, に can sometimes be omitted in casual Japanese. For 週末, both are possible depending on style and context:

• 週末に散歩します
• 週末散歩します

But using に is very natural and clear for learners.

で marks the place where an action happens.

Since 散歩します is an action, 公園で means:

• in the park
• at the park as the location of the walking

Compare the roles:

• に often marks a destination, time, or existence
• で marks the location where an action takes place

So:

• 公園で散歩します = take a walk in the park
• not go to the park

If you wanted to emphasize going to the park, you might use 公園に行きます.

In 一緒に, the に turns 一緒 into an adverbial expression meaning together.

So:

• 一緒 = together, the same company
• 一緒に = together, jointly

In this sentence, 一緒に tells us how they walk: they do it together.

This is a fixed and very common expression.

Examples:

• 一緒に行きます = go together
• 一緒に食べます = eat together

No, they have different jobs.

In this sentence:

• 週末に: に marks time
• 一緒に: に is part of an adverbial expression

So even though the particle is the same, its function depends on what comes before it.

This is very normal in Japanese. One particle can have several uses.

散歩します is the polite non-past form of 散歩する.

Breakdown:

• 散歩 = walk, stroll
• する = to do
• 散歩する = to take a walk
• 散歩します = polite form

The non-past form can mean:

• a present habitual action: they walk
• a future action: they will walk

So this sentence could mean:

• Those sisters walk together in the park on weekends
• or Those sisters will take a walk together in the park this weekend

The exact meaning depends on context.

Because there is no direct object here.

散歩する behaves like to take a walk or to go for a walk, so the sentence does not need a direct object.

Instead, it uses:

• 公園で for the place of the action
• 週末に for time
• 一緒に for manner

A related point: sometimes Japanese does use を with places to mark the route or area traveled through:

• 公園を散歩します

That means something like walk through the park.

But 公園で散歩します focuses on the park as the location where the activity happens.

Not completely. Japanese word order is more flexible than English, as long as the particles make the roles clear.

This sentence is:

• その姉妹は 週末に 公園で 一緒に 散歩します

You could also hear:

• その姉妹は 一緒に 週末に 公園で 散歩します
• その姉妹は 公園で 週末に 一緒に 散歩します

These all sound understandable, though some orders feel more natural depending on emphasis.

The verb usually comes at the end, and the particles show how the other parts connect.

Yes, it can be natural in Japanese if the sisters are already identified in the conversation or context.

For example, if people were already talking about a certain family, その姉妹 would mean those sisters.

Japanese often uses demonstratives like その where English might choose:

• the sisters
• those sisters
• or even no determiner at all depending on context

So while it may sound slightly formal or specific in isolation, it is grammatically fine and natural in the right context.

Yes. Because 散歩します is non-past, the sentence can mean either, depending on context.

Possible readings:

• habitual: Those sisters take walks together in the park on weekends.
• future: Those sisters will take a walk together in the park this weekend/weekend.

If you want to make the habitual meaning clearer, context usually does that. If you want to be very explicit about the future, other time expressions can help.

A casual version would usually end with 散歩する instead of 散歩します:

• その姉妹は週末に公園で一緒に散歩する。

In everyday speech, depending on context, Japanese might also drop the topic if it is already understood:

• 週末に公園で一緒に散歩する。

Japanese often omits information that is already clear, much more than English does.