depaato de ha, kodomotati ga esukareetaa de asobanai you ni, tenin ga yoku mite iru.

では is で + は.

• で marks the location where something happens.
• は adds a topic or contrast nuance.

So デパートでは means something like:

• in department stores
• as for department stores
• at department stores, ...

It often sounds a little broader than plain デパートで, as if the speaker is talking about what happens in that setting in general.

In this sentence, デパートでは sets the scene: In department stores, ...

Here, 子供たちが marks children as the ones doing the action in the subordinate clause:

• 子供たちがエスカレーターで遊ばないように
• so that children do not play on the escalator

The particle が is natural here because it identifies who would do the action 遊ぶ.

If you used は, it would sound more like you were making children the topic or contrastively talking about them. That is possible in some contexts, but が is the normal choice here inside this kind of clause.

So:

• 子供たちが = children are the ones who might play
• 店員が = store clerks are the ones who are watching

The sentence has two separate が subjects in two different parts of the sentence.

子供たち means children.

• 子供 can mean child or children, depending on context.
• たち explicitly makes it plural or collective.

So:

• 子供 = child / children
• 子供たち = children

In Japanese, plural markers are often optional. The speaker uses たち here to make it clear that they mean children in general, not just one child.

Because で has more than one common use.

1. デパートで(は)
   Here で marks the place where the situation happens:
   in/at the department store

2. エスカレーターで
   Here it marks the place or setting of the action 遊ぶ:
   on/at the escalator

So the two で particles do not mean exactly the same thing in English, but both are normal uses of で in Japanese.

A literal breakdown is something like:

• at department stores
• children on the escalator
• so that they do not play
• store clerks watch carefully

遊ばないように means so that they do not play or to prevent them from playing.

Breakdown:

• 遊ぶ = to play
• 遊ばない = do not play
• ように = so that / in order that

So:

• 遊ばないように = so that they won’t play
• in this sentence, more naturally: to make sure they do not play

This pattern is very common:

• 忘れないようにメモする
  I make a note so I won’t forget.
• 遅れないように早く出る
  I leave early so that I won’t be late.

Here the sentence is about prevention, so it has the sense of to prevent children from playing on the escalator.

Not exactly.

• 遊ばないように = so that they do not play
• 遊ばせないように = so that they are not allowed to play / so that someone does not let them play

The second one uses the causative form 遊ばせる and its negative 遊ばせない, which adds the idea of letting/making someone play.

In your sentence, 遊ばないように keeps the focus on the children’s action itself: the clerks watch so that the children do not play on the escalator.

Here 見ている means watching, keeping an eye on, or monitoring.

• 見る = to see / look
• 見ている = is watching / are watching / keep watching

In this sentence, 店員がよく見ている does not just mean the clerks happen to be looking at something. It means they are actively keeping watch.

So a natural interpretation is:

• The store clerks keep a close eye on things
• The store clerks watch carefully

Because the purpose is safety/prevention, 見ている has the nuance of supervising.

よく can mean different things depending on context.

Common meanings include:

• well
• carefully
• often

In this sentence, よく見ている most naturally means:

• watching carefully
• keeping a close watch

It may also suggest regularly/often, but the strongest nuance here is carefully because the sentence is about preventing dangerous behavior.

So よく見ている is not just see well. It means keep a careful eye on.

見ている is the -te iru form, which often shows:

• an ongoing action
• a continuing state
• a habitual action

Here it suggests that the clerks are watching/keeping watch as an ongoing or regular practice.

So the sentence means something like:

• Store clerks keep an eye on them
• Store clerks are watching carefully

If you said 店員がよく見る, it would sound less natural here and more like a simple general statement about the act of seeing.

The sentence has this basic structure:

[Place/topic] + [purpose/prevention clause] + [main clause]

More specifically:

• デパートでは
  In department stores,
• 子供たちがエスカレーターで遊ばないように、
  so that children do not play on the escalator,
• 店員がよく見ている。
  store clerks keep a close watch.

So the main action is:

• 店員がよく見ている = the store clerks are watching

And the earlier clause explains the purpose:

• 子供たちがエスカレーターで遊ばないように = to prevent children from playing on the escalator

Japanese often puts the reason, condition, or purpose before the main action.

Yes. 店員 by itself does not force singular or plural.

Depending on context, it can mean:

• a store clerk
• store clerks

In this sentence, English will usually translate it as store clerks because the sentence sounds like a general statement about what department store staff do.

Japanese often leaves singular/plural unstated unless it matters.

Not grammatically essential, but it helps readability.

The comma shows that:

• 子供たちがエスカレーターで遊ばないように is one chunk
• 店員がよく見ている is the main statement

Without the comma, the sentence is still understandable. With the comma, it is easier to see the purpose clause before the main clause.

Not quite. That translation misses an important part of the sentence.

The key point is not just that clerks watch children often. It is that they watch for a purpose:

• to prevent children from playing on the escalator

Also, よく見ている here is better understood as watching carefully / keeping a close eye on rather than simply often watch.

So the sentence is closer to:

• In department stores, the clerks keep a close eye on things so that children do not play on the escalator.

That captures both the purpose and the nuance of supervision.