kono syatu ha usui node, huyu ha kimasen.

They are doing two different topic-related jobs.

• このシャツは = As for this shirt, ...
• 冬は = in winter / as for winter, ...

The first は sets the main topic: this shirt.

The second は adds a contrastive topic: in winter. It suggests something like:

• In winter, I don't wear it
  and possibly implies:
• but in other seasons, I might.

So the sentence is not strange with two は particles. This is very common in Japanese.

冬は is used here to mark winter as a topic or contrastive time frame.

• 冬は着ません = As for winter, I don’t wear it
• This can imply contrast with other seasons.

If you said 冬に着ません, it would sound more like you are simply placing the action in time: I don't wear it in winter. That is possible in some contexts, but 冬は is more natural here because the sentence contrasts winter with other times of year.

So は is not just marking time; it adds a nuance of “at least in winter” or “when it comes to winter.”

ので means because or since.

In this sentence:

• 薄いので = because it is thin

So the whole sentence is:

• Because this shirt is thin, I don’t wear it in winter.

Compared with から, ので often sounds a little more neutral, explanatory, or gentle.

For example:

• 薄いから、冬は着ません。 = also correct, a bit more direct
• 薄いので、冬は着ません。 = slightly softer and more formal

Because 薄い is an い-adjective, and before ので it stays in its plain form:

• 薄い + ので → 薄いので

You do not change it to 薄く here.

Compare:

• い-adjective + ので
  • 寒いので = because it’s cold
  • 高いので = because it’s expensive
  • 薄いので = because it’s thin

But 薄く is used in other grammar patterns, such as adverbial use:

• 薄く切る = cut thinly
• 薄くなる = become thin

So in this sentence, 薄いので is the correct form.

Here, 薄い means thin.

For clothing, it usually means the material is not thick or warm enough. So this sentence means the shirt is too light/thin for winter.

Be careful, because 薄い can have several related meanings depending on context:

• 紙が薄い = the paper is thin
• 味が薄い = the flavor is weak/light
• 色が薄い = the color is pale

In this sentence, because it is about a shirt and winter, the meaning is clearly thin/lightweight.

The verb here is 着る（きる）, which means to wear clothing on the upper body, such as:

• shirts
• jackets
• coats
• dresses

So:

• 着ません = do not wear

This is the polite negative form of 着る.

It is not 着ける. 着ける（つける） is a different verb, usually meaning things like to attach, to put on accessories, or to switch on depending on context.

For clothing, Japanese uses different verbs depending on what you wear:

• 着る = wear on the upper body
• はく / 履く = wear on the lower body or on feet
• かぶる = wear on the head
• する = wear accessories like a tie, ring, watch

So シャツ goes naturally with 着る.

Japanese often leaves out the subject when it is clear from context.

So:

• このシャツは薄いので、冬は着ません。

naturally means something like:

• This shirt is thin, so I don’t wear it in winter.

Japanese does not need to explicitly say 私は if the speaker is obviously talking about their own habits or choices.

If you wanted to make it explicit, you could say:

• 私はこのシャツは薄いので、冬は着ません。

But that often sounds unnecessary unless you need contrast, such as:

• I don’t wear it in winter, but my sister does.

No, the meaning is the same. The difference is just spacing.

Normally Japanese is written without spaces:

• このシャツは薄いので、冬は着ません。

In learning materials, spaces are often added to make it easier to read:

• この　シャツ　は　薄い　ので、　冬　は　着ません。

Also, この must come directly before the noun it modifies:

• このシャツ = this shirt

You cannot say:

• このはシャツ
  or
• シャツこの

Yes. You could say:

• このシャツは薄いから、冬は着ません。

That also means Because this shirt is thin, I don’t wear it in winter.

The difference is mainly nuance:

• ので = a bit softer, more explanatory, somewhat more formal
• から = a bit more direct, conversational

Both are very common and natural. Learners should understand both.

No. Because of the earlier topic このシャツは, the sentence is about this particular shirt.

So the meaning is:

• I don’t wear this shirt in winter

It does not mean:

• I don’t wear shirts in winter
• I never wear anything in winter

The topic at the start controls what the later part refers to. Once このシャツ is introduced as the topic, the sentence keeps talking about that shirt.

Yes. ので can connect to different word types, but the form changes a little.

• い-adjective

  • 薄いので = because it is thin

• な-adjective

  • 静かなので = because it is quiet

• noun

  • 冬なので = because it is winter
  • 学生なので = because I am a student

• verb

  • 行くので = because I will go
  • 着ないので = because I do not wear it

So in your sentence, 薄いので is the normal い-adjective + ので pattern.