Learn Hardcore Japanese: siyakusyo de miti wo kiitara, sinsetuna keisatukan wo syoukaisite kuremasita. - When I asked for directions at city hall, they introduced a kind police officer to me.

くれる is used when someone does something for “me” (or for my in‑group).
That means:
- I asked for directions.
- Someone at city hall (staff, clerk, etc.) introduced a kind police officer for my benefit.

So the structure is:

I asked for directions at city hall,
then they kindly introduced a kind police officer to me.

Japanese doesn’t need to spell out “I” or “they” when it’s clear from context.

What does 聞いたら mean? How does ～たら work here?

聞いたら is:

聞いた (past form of 聞く) + ら (from ～たら)

～たら attached to a past tense verb often means “when … (happened), … (resulted)”.

So:

道を聞いたら、〜
≈ When I asked for directions, …
(a natural “when” with the nuance that B happened as a result of A)

Here 聞いたら is not a hypothetical “if I ask”; it’s a real past event:
“When I asked, they (then) introduced a kind police officer.”

Compare:

道を聞くと、親切な警察官を紹介してくれました。
Sounds more like a general rule/habit (“whenever I ask…”), and is odd for a one‑time past event.
道を聞いたとき、〜
More neutral “when I asked…”, slightly more formal/explicit than 聞いたら.

What is 親切な doing here, and why is it な and not い?

親切（しんせつ） is a な‑adjective (形容動詞), not an い‑adjective.

Dictionary form: 親切（な） – kind, helpful, considerate

For な‑adjectives, when they directly modify a noun, you add な:

親切な警察官 – a kind police officer
有名な人 – a famous person
静かな部屋 – a quiet room

If it were an い‑adjective, you would see い at the end, like:

優しい人 – a kind person (い‑adjective)

So 親切な警察官 is just “a kind police officer”, with 親切 describing 警察官 via the な linker.

What does 紹介してくれました mean exactly? How is it built?

紹介してくれました breaks down as:

紹介する – to introduce; to refer (someone to someone)
紹介して – て‑form of 紹介する
くれる – to give (to me / to us); to do (something) for me/us
くれました – polite past of くれる

Verb て + くれる = someone does that action for my benefit.

So:

親切な警察官を紹介してくれました。
= [They] introduced a kind police officer *for me (did me the favor of introducing one).*

Nuances:

Emphasizes the speaker’s benefit and gratitude.
Implies the subject (city hall staff, etc.) was helpful / did a considerate favor, not just a neutral action.

Why is there an を before 紹介してくれました? What is 親切な警察官を grammatically?

親切な警察官を is the direct object of 紹介してくれました.

Verb: 紹介する – to introduce (someone)
Direct object (the one being introduced): 親切な警察官

So:

親切な警察官を紹介してくれました。
= They introduced *a kind police officer (to me).*

The person being introduced to is not marked here (you), but understood:

Full form could be:
私に親切な警察官を紹介してくれました。
They introduced a kind police officer *to me.*

Who exactly is doing the introducing, and who is being introduced to whom?

The sentence is compact, so several roles are implied:

Speaker (I):
- Asks for directions (道を聞いたら).
- Is the beneficiary of the favor (くれる).
City hall staff / person at city hall:
- Is the subject of 紹介してくれました (the one doing the action).
- Introduces the police officer for the speaker.
Police officer:
- Is the object of 紹介する.
- Is the person you get introduced to.

So in natural English:

When I asked for directions at city hall, (a staff member there) kindly introduced me to a kind police officer.

Japanese leaves out “I”, “the staff member”, and “to me” because the roles are clear from context and from くれる (which tells us the action was done for the speaker).

What is the difference between using ～てくれる and ～てもらう here?

Both express receiving a favor, but the viewpoint is different.

～てくれる – emphasizes the giver:
- “[They] do X for me.”
- Pattern: [Giver] が／は + [Verb て] + くれる
～てもらう – emphasizes the receiver:
- “I receive X being done (by someone).”
- Pattern: [Receiver] が／は + [Giver] に／から + [Verb て] + もらう

In this sentence:

紹介してくれました。
– (Someone there) kindly introduced (the officer) for me.

You could also say:

市役所の人に親切な警察官を紹介してもらいました。
– I got a kind police officer introduced to me by the city hall staff.

Both mean essentially the same thing, but:

～てくれる = “They kindly did X (for me).”
～てもらう = “I received the favor of them doing X.”

The original sentence focuses on the helpers’ kindness (くれる) rather than on “I got something” (もらう).

Could 聞いたら be replaced by 聞いたとき or 聞くと? Would the meaning change?

You can replace it, but the nuance shifts:

聞いたら
- Natural, conversational.
- Means “when I asked (and then, as a result) …”
- Strong cause/result feeling.
聞いたとき
- More neutral “when”:
  - 道を聞いたとき、親切な警察官を紹介してくれました。
    When I asked for directions, they introduced a kind police officer.
- Slightly more formal or written‑style than 聞いたら.
聞くと
- Often used for general truths / habitual results:
  - When I ask, (always/usually) …
- For this specific one‑time past event, 聞くと can sound a bit like you’re describing a pattern rather than a single episode.

So 聞いたら is the most natural for a specific past event with a “this happened, then that happened” feeling, which matches the sentence.