sono sonzai wo sirimasendesita.

その is the determiner that before a noun.

So その存在 literally means that existence. In natural English, it is often translated as its existence or the existence of that thing, depending on the context.

A useful comparison:

• この = this
• その = that
• あの = that over there / that one we both know

In this sentence, その usually refers to something already mentioned in the conversation or text.

存在 means existence.

It is a noun, and it sounds a bit formal or abstract compared with very everyday wording. So その存在 is literally that existence.

Japanese often uses abstract nouns like this in places where English might use a simpler phrasing. So even if the Japanese says existence, the most natural English translation may just be I didn’t know about it or I didn’t know it existed.

を marks the direct object of the verb 知る.

Here, the thing being known is その存在, so it gets を:

• その存在 = that existence
• を = object marker
• 知りませんでした = did not know

So the structure is basically:

[that existence] + object marker + [did not know]

In English, we often say know of its existence or know that it exists, but in Japanese it is very normal to say 存在を知る.

Because 知りませんでした is the polite past negative form.

• 知りません = do not know / don’t know
• 知りませんでした = did not know

This sentence is talking about a past situation, so でした is needed.

If you wanted a casual version, you could say:

• その存在を知らなかった。

That means the same thing, but in plain style instead of polite style.

It can mean both, depending on the form and context.

This is a very common point of confusion.

• 知る as a dictionary form can mean to know or to learn/find out
• 知っている is often used for the state of knowing
• but in negative forms, 知らない / 知りません very naturally mean don’t know
• and 知りませんでした naturally means didn’t know

So in this sentence, you should understand 知りませんでした simply as did not know.

Because 知りませんでした is the normal, natural way to say didn’t know here.

With 知る, the negative forms often behave more simply:

• 知りません = I don’t know
• 知りませんでした = I didn’t know

You will often learn that 知っている means know, and that is true, but that does not mean you must always make the negative with 知っていない. In real Japanese, 知りません and 知りませんでした are extremely common and natural.

The subject is omitted, which is very normal in Japanese.

Depending on context, it could mean:

• I didn’t know
• we didn’t know
• he/she/they didn’t know

But if this sentence appears by itself, many learners would naturally read it as I didn’t know, because that is a common default in translation.

Japanese often leaves out subjects when they are already understood from the situation.

Yes, it is at least somewhat formal.

There are two reasons:

• 知りませんでした is polite です／ます style
• 存在 is a slightly formal or abstract noun

So the sentence sounds more formal than a casual everyday line like:

• その存在を知らなかった。

It is still perfectly natural Japanese, especially in writing, explanations, speeches, or serious conversation.

Yes, but the nuance changes.

• その存在を知りませんでした。 = neutral statement: I didn’t know of its existence
• その存在は知りませんでした。 = puts its existence into focus or contrast, like As for its existence, I didn’t know

So を is the straightforward object marker, while は adds a topic or contrast feeling.

Those spaces are just for learners.

Normally, Japanese is written without spaces:

その存在を知りませんでした。

Japanese sentences are usually not separated by spaces the way English words are. Educational materials often add spaces to help beginners see the parts more clearly.