Learn Hardcore Japanese: kinou tomodati kara messeezi ga kimasita. - Yesterday I received a message from a friend.

In this sentence, it’s clear in a normal conversation that the person speaking is the one who got the message, so saying 私(わたし)は is not necessary.

You can say:

昨日、私は友達からメッセージが来ました。

but it sounds a bit heavy or overly explicit in most everyday contexts.
More natural would be:

昨日、友達からメッセージが来ました。 (subject understood as “I”)

What does から mean after 友達, and why is it used here?

から is a particle that often means “from”.

In this sentence:

友達から = from (a) friend / from my friend

So it marks the source of the message, the person it comes from.
This is a very common pattern:

先生からメールが来ました。 – A mail came from my teacher.
会社から電話がありました。 – There was a phone call from the company.

Could we say 友達に instead of 友達から here?

In this context, 友達から is the natural choice.

友達からメッセージが来ました。
Focus: The message came from the friend (source).

友達に generally means “to a friend / for a friend”, and is used when you are doing something to your friend:

友達にメッセージを送りました。 – I sent a message to my friend.

So:

友達からメッセージが来ました。 – A message came from my friend.
友達にメッセージを送りました。 – I sent a message to my friend.

They’re mirror images with から (from) and に (to).

Why is が used with メッセージ? Isn’t “message” the object, not the subject?

In English we think: I received a message (subject = I, object = message).

Japanese is structured differently here. The sentence is more like:

“As for yesterday / from my friend, a message came.”

So:

メッセージが来ました。
literally = “A message came.”

Here メッセージ is treated as the subject of the verb 来ました (“came”), so it takes が.

You could conceptually rephrase in English as “A message arrived” to match the Japanese grammar better.

Why use 来ました (“came”) instead of something like “received” (もらいました)?

Japanese often describes messages, calls, mail, etc. as if they come/arrive to you, not as you actively receiving them.

Common patterns:

メッセージが来ました。 – A message came (I got a message).
メールが届きました。 – An email arrived (I received an email).
電話がありました。 – There was a phone call.

You can say:

友達からメッセージをもらいました。 – I received a message from my friend.

That’s also natural, but:

メッセージが来ました。 sounds very common and neutral.
メッセージをもらいました。 focuses more on you receiving it.

Both are OK; this sentence just uses a very standard way of talking about messages.

Can 昨日 (yesterday) move to a different position in the sentence?

Yes. 昨日 is a time expression and can move quite freely as long as it’s clear and natural. Some common options:

昨日、友達からメッセージが来ました。
友達から昨日メッセージが来ました。
友達からメッセージが昨日来ました。 (possible, but sounds a bit marked/emphasized)

The first one (昨日、友達から…) is probably the most natural and neutral.

You generally avoid splitting 昨日 too far away from the verb in complicated sentences, but in simple ones like this there is flexibility.

Why doesn’t 昨日 have a particle like は or に?

Time expressions in Japanese (like 昨日, 今日, 明日, 毎日) are often used without any particle when they simply answer “when?”.

So all of these are normal:

昨日、映画を見ました。 – I watched a movie yesterday.
今日、仕事があります。 – I have work today.

You can add particles for nuance:

昨日は友達からメッセージが来ました。
Here 昨日は makes “yesterday” the topic, something like:
“As for yesterday, I got a message from a friend.”
(implying contrast with other days, or setting “yesterday” up as the frame).

But in the original sentence, 昨日 without a particle is perfectly normal and very common.

Does 友達 mean “a friend,” “my friend,” or “friends” here?

Japanese usually doesn’t mark singular vs plural unless it’s important, and it also often omits “my/your/etc.” when obvious.

So 友達 by itself can mean:

a friend
my friend
(some) friends

In this sentence, native speakers will simply assume the most natural reading from context, usually:

“(One of) my friends”

If you really need to specify plural, you can say:

友達たち (friends) – used, but not as often as you might expect.
or specify with a number: 友達二人, 友達何人か, etc.

What politeness level is 来ました, and how is it different from 来た?

来ました is the polite past form of 来る (to come):

来ます – (it) comes / will come (polite)
来ました – (it) came (polite)

来た is the plain past form:

来た – (it) came (plain / casual)

So:

昨日、友達からメッセージが来ました。 – Polite, suitable for talking to strangers, teachers, etc.
昨日、友達からメッセージが来た。 – Casual, used with friends, family, people of equal status.

Could I say メール or LINE instead of メッセージ?

Yes. Japanese uses many loanwords for digital communication.

Examples:

昨日、友達からメールが来ました。 – I got an email from a friend yesterday.
昨日、友達からLINEが来ました。 – I got a LINE message from a friend yesterday.

Note:

メッセージ is a general “message” (could be SMS, DM, app message, etc.).
メール often means “email”, but in casual speech it might also refer to text messages.
LINE(ライン) is the popular messaging app in Japan; LINEが来た is very natural.

How would I say “I didn’t get a message from my friend yesterday” using the same pattern?

Just change the verb to its negative past polite form:

来ませんでした = did not come

So:

昨日、友達からメッセージが来ませんでした。
= I didn’t get a message from my friend yesterday.

Casual version:

昨日、友達からメッセージが来なかった。

Is it okay to omit メッセージが and just say 友達から来ました?

Normally, no, that sounds incomplete or confusing if it stands alone.

友達から来ました。 by itself would usually mean
“I came from my friend” or “(something/someone) came from my friend,”
but it feels like it’s missing what exactly came.

In the original sentence, メッセージ is the thing that comes, so you need it (or another noun like メール, LINE, etc.):

友達からメッセージが来ました。 – A message came from a friend.

You can omit メッセージ only if it’s extremely clear from context, and even then people usually say at least:

友達から来たよ。 – (The message/thing we mentioned) came from my friend.

in follow-up to an already established topic.

Can I also say メッセージを受け取りました? Is that different from メッセージが来ました?

Yes, 受け取る means “to receive” (physically or metaphorically), so:

友達からメッセージを受け取りました。 – I received a message from my friend.

This is correct, but it sounds a bit more formal or literal than what people usually say in everyday chat.

In daily conversation:

メッセージが来ました。
メッセージが届きました。

are more natural and more commonly used.
受け取りました is fine, just slightly more “I formally received it” in feeling.