Learn Hardcore Japanese: kurai uti ni okite sanpo wo suru to, asa no kuuki ga totemo kimotiii desu. - If I get up and take a walk while it’s still dark, the morning air feels really pleasant.

[plain form] + うちに = “while … is still the case / before that situation changes”
- verb (dictionary form): 雨が降っているうちに – while it is still raining
- i-adjective: 若いうちに – while you are still young
- na-adjective + な: 元気なうちに – while (you are) still energetic
- noun + の: 学生のうちに – while (you are) a student

So 暗いうちに focuses on doing something before it stops being dark (i.e., before sunrise), not just “at some random time when it’s dark.” It implies “while it’s still dark / before it gets light.”

The spaces in the sentence are just word-separators; you should read it as one grammar chunk: 暗いうちに.

How is うちに different from とき (as in 暗いとき)? Could I say 暗いときに起きて… instead?

Both can be translated as “when/while,” but the nuance is different.

暗いときに…
- Literally “when it is dark…”
- Just describes the time condition: “at times when it’s dark.”
- No special nuance about “before it changes.”
暗いうちに…
- “While it is still dark / before it stops being dark.”
- Strong nuance of “before the situation changes”, i.e. before it gets light.

In your sentence, 暗いうちに起きて散歩をすると… suggests:

You intentionally get up and walk before sunrise, while it is still dark.

If you say 暗いときに起きて散歩をすると…, it’s grammatically OK, but it sounds more like a general statement about times when it happens to be dark, without that “before dawn” feeling.

Why is うち written in hiragana and not as the kanji 家 here?

When うち means “home / house / my place”, it’s usually written 家.

But in the grammar pattern X うちに (“while X is still the case / before X changes”), うち is an abstract noun like “inside / within that time-frame / within that state,” and it’s normally written in hiragana:

若いうちに – while you are still young
雨が降っているうちに – while it’s still raining
学生のうちに – while you are still a student

So here 暗いうちに is the grammar pattern, not “dark house,” so it stays in hiragana.

What exactly is the function of 起きて here? Does it mean “and then,” “after,” or something else?

起きて is the て-form of 起きる and here it’s a linking form meaning “(I) get up and …”.

In Japanese, the て-form can link actions in several ways, often corresponding to English “and (then)”:

起きて　散歩をする
→ “(I) get up and (then) take a walk.”

Depending on context, Vて can mean:

simple sequence: “do A and (then) do B”
cause: “do A and (so) B happens”
manner: “do A and (in that way) B”

Here it’s straightforward sequence.

You could also say:

暗いうちに起きてから散歩をすると…
→ “If I get up while it’s still dark and after that go for a walk, …”

起きてから makes the “after that” relationship very explicit, but the original 起きて散歩をする already naturally implies that order, so it’s often left as simple て-form.

What does 散歩をする literally mean, and how is it different from 散歩する?

散歩 is a noun meaning “a walk / strolling.”
する is the verb “to do.”

散歩をする = “to do a walk” → “to go for a walk / to take a walk.”

About 散歩をする vs 散歩する:

Both are correct and mean the same thing.
散歩をする is slightly more explicit and somewhat more “careful” or textbook-y.
散歩する is a bit more compact and is also very common.

In speech and writing, you will see both. In casual conversation people probably say 散歩する slightly more often, but 散歩をする does not sound unnatural at all.

Why is there a と after 散歩をする? Is this the same と as in quotations (like 「…」と言う)?

The と here is not the quotative と. It is the conditional と, which often translates as “when” or “if”.

Pattern:

[plain form] と、[result].

It’s used for:

automatic / natural results
- 春になると、暖かくなります。 – When spring comes, it gets warm.
habitual / general truths
- このボタンを押すと、ドアが開きます。 – If you press this button, the door opens.

In your sentence:

暗いうちに起きて散歩をすると、朝の空気がとても気持ちいいです。
→ Roughly: “When / If I get up while it’s still dark and take a walk, the morning air feels very pleasant.”

So:

と here marks that what comes after is a natural or usual result of what comes before.
It’s different from と after 言う / 思う, which introduces quoted content.

Why is 朝の空気 marked by が instead of は? Could I say 朝の空気はとても気持ちいいです?

Yes, you could say 朝の空気はとても気持ちいいです, and it would be correct. The nuance changes slightly:

朝の空気がとても気持ちいいです。
- が marks the subject.
- Feels like: “It is the morning air that feels very pleasant.”
- In context with the と-clause, it often sounds like a natural result or discovery:
  - “(When I do X,) the morning air (I experience then) is very pleasant.”
朝の空気はとても気持ちいいです。
- は marks the topic: “As for the morning air, it is very pleasant.”
- Sounds more like a general statement about morning air, independent of any specific condition.

With [clause] と、[result], using が in the result clause is very natural, because it clearly ties “morning air” as the subject of the resulting feeling.

Why is it 気持ちいい and not 気持ちがいい? Are both correct?

The basic, “full” form is:

気持ちがいい – literally: “The feeling is good.” → “It feels good / pleasant.”

In everyday speech, 気持ちがいい is very often shortened to:

気持ちいい (or 気持ちい, more casual), dropping the が.

So:

朝の空気がとても気持ちがいいです。 – fully explicit
朝の空気がとても気持ちいいです。 – natural, common in speech and casual writing

Both are grammatically correct and mean the same.
The contracted 気持ちいい feels slightly more casual/colloquial; 気持ちがいい is fine in both casual and formal contexts.

What is the role of the final です here? Could the sentence end at 気持ちいい?

です is the polite copula, making the sentence polite.

気持ちいい is a plain form (casual) predicate.
気持ちいいです is the polite version in standard polite speech.

So:

朝の空気がとても気持ちいい。
→ Plain / casual: “The morning air feels really nice.”
朝の空気がとても気持ちいいです。
→ Polite: same meaning, but appropriate in most everyday polite situations.

Which one you use depends on:

Who you’re talking to
The level of formality you want

In textbooks, sentences are often given in polite form, so ending with です is standard there.

What does 朝の空気 literally mean, and what is the function of の here?

朝の空気 is:

朝 – “morning”
の – possessive/attributive marker
空気 – “air”

Literally: “morning’s air”, i.e., “morning air.”

The の here:

links two nouns (朝 and 空気),
showing that 朝 is describing/qualifying 空気.

This pattern is extremely common:

日本の音楽 – Japanese music
冬の夜 – a winter night
公園のベンチ – a bench in the park / the park’s bench

Is there any special reason the sentence says 散歩をする instead of a more basic verb like 歩く?

Yes, there is a nuance difference:

歩く – “to walk” (the act of moving by foot)
散歩をする – “to go for a walk / stroll,” which implies:
- walking for pleasure / relaxation, not just movement.

So:

駅まで歩く。 – I walk to the station. (mode of transportation)
公園を散歩する。 – I stroll around the park. (for enjoyment)

In your sentence, the idea is not just “walking” as transportation, but taking a walk as an activity, so 散歩をする is more natural than simply 歩く.

Can you summarize the overall structure of the sentence and how the pieces fit together grammatically?

Yes. Broken down:

暗いうちに
- 暗い (dark, i-adjective) + うちに (“while / before it changes”)
  → “while it is still dark / before it gets light”
起きて散歩をする
- 起きて – get up (て-form, linking)
- 散歩をする – go for a walk
  → “(I) get up and go for a walk”
[起きて散歩をする] と、
- と – conditional “when/if,” marking what follows as the resulting situation
  → “when / if (I) get up while it’s still dark and go for a walk,”
朝の空気が
- 朝の空気 – the morning air (朝 + の + 空気)
- が – subject marker
  → “the morning air (as subject)”
とても気持ちいいです。
- とても – very
- 気持ちいい(です) – feels pleasant / nice (polite)
  → “feels very pleasant.”

All together:

Conditional clause with と:
暗いうちに起きて散歩をすると、
Result clause:
朝の空気がとても気持ちいいです。

Grammatically:
[Condition (plain form) + と] + [Result (が-marked subject + adjective + です)].