Learn Hardcore Japanese: reitouko ni gohan ga aru node, isogasii yoru mo ansin desu. - Since there is rice in the freezer, I feel at ease even on busy nights.

に → location of existence
- 冷凍庫にご飯がある。
  There is rice in the freezer.
で → location where an action takes place
- レストランでご飯を食べる。
  I eat rice at a restaurant.

Since ある is an existence verb, you must use に, not で.

Why is ご飯 marked with が and not は?

In 冷凍庫にご飯がある, the focus is on what exists in the freezer. The pattern XにYがある uses が to mark the thing that exists.

ご飯が → rice (as the thing that exists)

If you said ご飯は冷凍庫にある, you are now talking about rice in general (topic), and saying where it is:

ご飯は冷凍庫にある。
As for the rice, it’s in the freezer. (Maybe in contrast to something else.)

In this sentence, the natural, neutral way is:

冷凍庫にご飯があるので…
Because there is rice in the freezer…

So が fits the standard “there is X” pattern.

Why is ある used and not いる?

Japanese has two basic existence verbs:

ある – for inanimate things (objects, places, plants, abstract things)
いる – for animate beings (people, animals)

ご飯 (rice/meal) is an inanimate thing, so you use ある:

冷凍庫にご飯がある。
There is rice in the freezer.

If it were a person or an animal, you’d use いる:

冷凍庫に猫がいる。
There is a cat in the freezer. (…hopefully not!)

Isn’t it strange that the first part uses ある (plain) but the second part has 安心です (polite)? Can you mix styles like that?

This mixture is very common and natural in Japanese.

Clause 1: 冷凍庫にご飯があるので、 → uses plain ある
Clause 2: 忙しい夜も安心です。 → uses polite です

You can also say:

冷凍庫にご飯がありますので、忙しい夜も安心です。

Both are grammatically correct. Nuances:

Plain form + ので sounds neutral and is very common in conversation and writing.
Polite form + ので (ありますので) sounds a bit more formal/businesslike.

So the original sentence is perfectly fine and very natural.

What is the nuance of ので here? How is it different from から?

Both ので and から can mean “because / since”, but there are nuance differences:

ので
- Softer, a bit more formal or polite.
- Often feels more objective or explanatory.
- Fits well with です/ます style.
から
- More direct and casual, especially in speech.
- Can sometimes sound like you’re giving a reason or excuse more bluntly.

In this sentence:

冷凍庫にご飯があるので、忙しい夜も安心です。
Since there is rice in the freezer, (we) can be at ease even on busy nights.

You could also say:

冷凍庫にご飯があるから、忙しい夜も安心です。

That’s also correct, but ので here fits the gentle, explanatory feel.

How does 忙しい work with 夜? Is it like English word order “busy night”?

Yes, 忙しい夜 is literally “busy night”, with the adjective before the noun, like in English.

忙しい – busy
夜 – night
忙しい夜 – a busy night / busy nights

Adjectives in Japanese typically go before the noun they modify:

新しい本 – a new book
小さい部屋 – a small room
長い一日 – a long day
忙しい夜 – a busy night

So 忙しい夜も安心です = Even on busy nights, (we) are at ease.

What does も in 忙しい夜も安心です add to the meaning?

も usually means “also / too / even.”

Here, the nuance is “even on busy nights”:

夜も安心です。
We’re at ease at night too.
忙しい夜も安心です。
We’re at ease even on busy nights.

So も implies something like:

Maybe on normal nights we’re already fine,
and even when it’s busy, we’re still okay because there is rice in the freezer.

It highlights that busy nights are not an exception; they’re included in the times when you can feel安心.

What does 安心です literally mean? Why is it not a verb like “to feel safe”?

安心 (あんしん) is a noun meaning relief / peace of mind / feeling safe.

In Japanese, a very common pattern is:

Noun + です → “it is [noun]”, but often translates as “to be [adjective] / to feel [adjective]” in English.

So:

安心です。
- Literally: “It is安心.”
- Natural English: “(I/We) feel at ease / don’t have to worry / it’s reassuring.”

Other examples of this pattern:

安全です。 – It is safe.
便利です。 – It is convenient.
簡単です。 – It is easy.

In context:

忙しい夜も安心です。
Even on busy nights, (we) don’t have to worry / can feel at ease.

Who is it that is “安心”? There is no I or we in the sentence. How do we know?

Japanese often omits the subject when it’s clear from context.

The sentence:

冷凍庫にご飯があるので、忙しい夜も安心です。

Literally just says:

Because there is rice in the freezer, even on busy nights is安心.

There’s no explicit I or we, but a natural interpretation in context is:

(私は / 私たちは) 忙しい夜も安心です。
I / we can be at ease even on busy nights.

Who it refers to (I, we, family, household, etc.) depends on the surrounding conversation. Japanese relies heavily on context instead of repeating pronouns.

Does ご飯 here mean “rice” or “meal”? How should I understand it?

ご飯 (ごはん) has two common meanings:

Cooked rice
A meal (generally, especially a main meal like lunch/dinner)

In context:

冷凍庫にご飯がある
likely means “there is cooked rice in the freezer”, often frozen portions of rice.

However, you could also interpret it more loosely as:

There are meals (frozen food) in the freezer, so busy nights are easy.

In daily conversation, native speakers often understand from context:

Talking specifically about rice → “cooked rice”
Talking more broadly about what to eat → “meal / food”

Here, both cooked rice in the freezer and something ready to eat in the freezer are reasonable interpretations, but cooked rice is the most literal.