tatami no heya no osiire ni huton wo simau to, heya wo hiroku tukaeru.

Because の links nouns together, and Japanese often builds longer noun phrases that way.

In this sentence:

• 畳の部屋 = a tatami room / a room with tatami
• 部屋の押し入れ = the room’s closet
• So 畳の部屋の押し入れ = the closet of the tatami room

You can think of it as layers:

• 畳 → 部屋: what kind of room? A tatami room.
• 部屋 → 押し入れ: which closet? The room’s closet.

So the repeated の is not unusual; it is just connecting nouns step by step.

畳の部屋 literally means a room with tatami mats. It describes the room by one of its features.

和室 means a Japanese-style room, which often has tatami, but can imply a broader traditional Japanese style.

So:

• 畳の部屋 focuses on the tatami flooring.
• 和室 focuses on the room being Japanese-style.

In many real situations they may refer to the same kind of room, but the nuance is slightly different.

押し入れ is a Japanese-style built-in storage space, especially common in tatami rooms. It is often used for storing 布団, blankets, and other bedding.

It is often translated as closet, but it is not exactly the same as a typical Western clothes closet. In context, 押し入れ strongly suggests the kind of storage space where futons are put away during the day.

Because に marks the destination of the action しまう.

• 押し入れにしまう = put away into the closet

Here, 布団 is the thing being put away, and 押し入れ is the place it goes to.

So:

• 押し入れに = into the closet
• 布団を = the futon
• しまう = put away / store

Because 布団 is the direct object of しまう.

• 布団をしまう = put away the futon

The action is being done to the futon, so を marks it.

Not exactly. しまう usually means put away, store, or tidy away.

So 布団をしまう is not just put the futon somewhere. It has the nuance of putting it away in its proper storage place.

This is why it fits naturally with 押し入れ.

Here, と is a conditional meaning when or if.

• 布団をしまうと、部屋を広く使える。
• If/when you put the futon away, you can use the room more spaciously.

This と is often used when the second part is a natural result, regular consequence, or general truth.

So it sounds like:

• Whenever you put the futon away, the result is that the room can be used more freely.

Yes, たら is possible, but the nuance changes a little.

• しまうと sounds like a natural or general result.
• しまったら sounds more like once you put it away or if you put it away in a specific situation.

Compare:

• 布団をしまうと、部屋を広く使える。
  = Generally speaking, putting the futon away makes the room usable more spaciously.

• 布団をしまったら、部屋を広く使える。
  = Once you’ve put the futon away, you can use the room more spaciously.

So と is a good choice if the speaker is stating a regular fact.

Because the two 部屋 words play different roles:

• 畳の部屋の押し入れ = the closet belonging to the tatami room
• 部屋を広く使える = can use the room spaciously

The first 部屋 is inside a noun phrase describing 押し入れ.
The second 部屋 is the object of 使える.

Japanese often repeats nouns where English might use it or restructure the sentence. Repeating 部屋 here is natural and clear.

Because 広く is the adverbial form of 広い.

• 広い = wide / spacious
• 広く = widely / spaciously

Here it modifies 使える:

• 部屋を広く使える = can use the room spaciously / can make better use of the room’s space

So 広く describes how the room can be used.

Literally, it means something like:

• can use the room widely
• can use the room in a spacious way

In natural English, that often becomes:

• can use the room more spaciously
• can make better use of the room
• can free up space in the room

So the Japanese is focusing on the manner of use: the room becomes more open and usable.

使える is the potential form of 使う.

• 使う = use
• 使える = can use / be able to use

So:

• 部屋を広く使う = use the room spaciously
• 部屋を広く使える = can use the room spaciously

The sentence is talking about what becomes possible after putting the futon away.

Good question. With potential expressions, が is often used for the thing that becomes possible, but を is also very common in modern Japanese, especially with verbs like 使える, 読める, 見られる, etc.

Here:

• 部屋を広く使える is natural and common.

Also, を makes good sense because 部屋 is still the thing being used.

So while learners are often taught potential + が, real Japanese frequently allows を as well.

Yes. Japanese often omits the subject when it is obvious or not important.

This sentence does not say exactly who puts away the futon or who can use the room more spaciously. Depending on context, it could mean:

• you
• we
• one
• people in general

That kind of omission is very normal in Japanese.

Because Japanese nouns usually do not show number unless it matters.

• 布団 can mean a futon or futons, depending on context.

In this sentence, English may translate it as the futon or futons, but Japanese leaves that open unless there is a need to be specific.

The same is true for many Japanese nouns.

It can be understood either way, depending on context.

Without extra context, it sounds like a general statement:

• If you put the futon away in the closet of a tatami room, you can use the room more spaciously.

But in a real conversation, it could also refer to a specific room already known to both speakers.

Japanese often leaves that distinction unstated unless it needs to be explicit.