ame no yoru ha zyoukyaku ga ooi node, untensyu mo isogasisou desita.

雨の夜 literally means a night of rain.

In natural English, that usually becomes a rainy night or on a rainy night.

Here, の connects two nouns:

• 雨 = rain
• 夜 = night

So 雨の夜 is a noun phrase meaning a rain-night / a night with rain.

This is a very common use of の in Japanese: it links nouns in a way that can mean of, with, for, or something adjective-like depending on context.

Examples:

• 日本の車 = Japanese car / car of Japan
• 冬の朝 = winter morning
• 雨の夜 = rainy night

は marks 雨の夜 as the topic or setting of the sentence.

So 雨の夜は gives a sense like:

• As for rainy nights...
• On rainy nights...

It sets up the situation the rest of the sentence is talking about.

A rough structure is:

• 雨の夜は = on rainy nights / when it is a rainy night
• 乗客が多い = there are many passengers
• ので = so / because
• 運転手も忙しそうでした = the driver also looked busy

So は helps frame the whole sentence around rainy nights.

Here, が marks 乗客 as the subject of 多い.

So 乗客が多い means:

• there are many passengers
• passengers are numerous

Why not は?

Because the main topic of the sentence is already 雨の夜は. Inside that topic, the sentence describes what is true: the passengers are many.

Using が here is very natural for introducing or identifying what has the property 多い.

Compare:

• 雨の夜は、乗客が多い。
  = On rainy nights, there are many passengers.

• 乗客は多い。
  = As for passengers, they are many.
  This sounds more like passengers are the main topic, which is not the focus here.

No. In 乗客が多い, 多い is the predicate of the clause, not a direct modifier before the noun.

So this does not mean:

• many passengers as a single noun phrase

Instead, it means:

• the passengers are many
• there are many passengers

If you want to say many passengers directly before a noun, you would usually say:

• 多くの乗客 = many passengers

So:

• 乗客が多い = there are many passengers
• 多くの乗客 = many passengers

ので means because or so.

In this sentence:

• 乗客が多いので、運転手も忙しそうでした。
• Because there were many passengers, the driver also looked busy.

Compared with から, ので often sounds:

• a little softer
• more explanatory
• more objective

Very roughly:

• から can sound more direct or personal
• ので can sound more neutral or matter-of-fact

Examples:

• 雨なので、行きません。 = Because it’s raining, I won’t go.
• 雨だから、行きません。 = Because it’s raining, I won’t go.

Both are correct, but ので often sounds a bit gentler.

This is a very common Japanese pattern.

In Japanese, only the final predicate of the sentence usually shows the politeness level. Clauses before it are often in plain form.

So:

• 乗客が多いので = plain form inside the reason clause
• 忙しそうでした = polite past at the end of the sentence

This is normal and natural.

That means the sentence is not mixing styles incorrectly. It is following the usual rule:

• non-final clauses: often plain
• final clause: polite if the sentence is in polite style

So 多いので、忙しそうでした is exactly what you would expect in polite Japanese.

も means also, too, or as well.

So 運転手も忙しそうでした means:

• the driver also looked busy
• the driver, too, looked busy

The nuance is that the situation affected not just one thing. Since there were many passengers, the driver was also busy-looking.

It can imply something like:

• there were many passengers,
• and the driver was affected as well

Without も, it would simply say:

• 運転手は忙しそうでした = the driver looked busy

With も, there is more of a sense of too / as well.

忙しそう means looks busy or seems busy.

It uses the appearance そう pattern, which is used when something seems a certain way based on what you can observe.

Formation:

• 忙しい → remove the final い
• 忙し
  • そう
• 忙しそう

Other examples:

• おいしい → おいしそう = looks delicious
• 暑い → 暑そう = looks hot
• 眠い → 眠そう = looks sleepy

So 忙しそうでした means:

• looked busy
• seemed busy

This does not necessarily mean the speaker knows for a fact that the driver was busy. It describes the speaker’s impression.

No. Japanese has two common そう patterns, and they are different.

1. Appearance そう
   = looks/seems ...

   • 忙しそう = looks busy
   • 雨が降りそう = looks like it’s going to rain

2. Hearsay そうです
   = I heard that... / they say that...

   • 忙しいそうです is not correct for hearsay
   • 忙しいそうです should actually be 忙しいそうです? No: for hearsay with an i-adjective, it is 忙しいそうです in some learner misconceptions, but the correct standard form is 忙しいそうです?
     The important point is: this sentence is clearly the appearance type because it is 忙しそう.

A simple way to tell them apart:

• busy-looking → 忙しそう
• I heard he is busy → 忙しいそうです is the hearsay pattern

In your sentence, it means looked busy, not I heard the driver was busy.

They mean different things.

• 忙しそうでした = looked busy / seemed busy
• 忙しかったです = was busy

So the sentence chooses 忙しそうでした because the speaker is describing an appearance or impression, not stating the driver’s actual condition as a fact.

Also, grammatically, そう behaves like a na-adjective-like form here, so its polite past is:

• 忙しそうです = looks busy
• 忙しそうでした = looked busy

Not:

• 忙しそうかった ✘

Plain past would be:

• 忙しそうだった

This is a great question, because Japanese often does this.

多い in 乗客が多いので can sound like a general or situational fact:

• on rainy nights, passengers are many

Then the main clause gives the speaker’s past observation:

• the driver looked busy

So the sentence can feel like:

• Because rainy nights tend to have many passengers, the driver also looked busy.

Japanese non-past form does not only mean future or present. It can also express:

• a general truth
• a habitual situation
• a scene-setting fact

If the speaker wanted to focus more on one specific past occasion, they might also say:

• 乗客が多かったので、運転手も忙しそうでした。

That would mean:

• Because there were many passengers, the driver also looked busy.

So the original 多いので is not wrong at all; it just sounds a bit more like a general condition or characteristic of rainy nights.