tomodati ha kuukou de ane wo miokutte kara, hitori de ie ni kaetta.

は marks 友達 as the topic of the sentence: as for the friend...

Here, the sentence is telling you what happened with that friend. If you used が instead, it would sound more like you are identifying or emphasizing the subject: the friend is the one who...

So:

• 友達は... = As for the friend...
• 友達が... = The friend is the one who...

Both can be grammatical, but は is the more natural choice here for a plain narrative sentence.

で marks the place where an action happens.

In this sentence, the action 見送る happened at the airport, so you say:

• 空港で見送る = to see someone off at the airport

A helpful comparison:

• に often marks a destination or point of existence
• で marks the location of an action

So here, the airport is not the goal of 帰る; it is the place where the seeing-off happened.

Because を marks the direct object of the verb, and direct objects can be people.

Here, 姉 is the person being seen off:

• 姉を見送る = to see older sister off

So を does not mean the object has to be a thing. It just marks what the action is directed toward.

It is made of:

• 見送る = to see someone off
• てから = after doing...

So 見送ってから means:

• after seeing her off
• after seeing the older sister off

This pattern shows that the first action is completed before the second action happens.

In this sentence:

1. the friend saw the older sister off at the airport
2. after that, the friend went home alone

Japanese often links actions by putting earlier verbs into a connecting form, while the final verb carries the main tense.

Here:

• 見送ってから connects the first action to the next one
• 帰った is the final verb, so it tells you the whole sequence is in the past

So even though 見送る is not written as 見送った here, the sentence still clearly means that both actions happened in the past.

一人で means alone or by oneself.

So:

• 一人で家に帰った = went home alone

It tells you the manner in which the friend went home: not with someone else, but alone.

It is the same particle, but the role is a little different.

• 空港で: で marks the place where the action happens
• 一人で: で marks the state/manner in which the action is done

So in this sentence, で is used twice:

• 空港で = at the airport
• 一人で = alone

This is very common in Japanese. The same particle often has related but slightly different uses.

Both are possible.

With 帰る, に is very common because it marks the destination directly:

• 家に帰る = go home / return home

へ is also possible and puts a little more focus on the direction:

• 家へ帰る = go toward home / head home

In everyday Japanese, 家に帰る is probably the most standard way to say it.

Japanese often leaves out possessive words like his, her, or my when the meaning is clear from context.

So 姉 here is understood from the situation. In a sentence like this, it most likely means the friend’s older sister.

One nuance learners should know: in real-life usage, 姉 often refers to the speaker’s own older sister when talking to other people. For someone else’s older sister, Japanese often uses お姉さん. But in narration or textbook-style sentences, family words can be interpreted from the sentence context more flexibly.

So for this sentence, you should read it according to the intended meaning shown to you.

Japanese word order is fairly flexible because particles show each word’s role.

For example, these are close in meaning:

• 友達は空港で姉を見送ってから、一人で家に帰った。
• 友達は姉を空港で見送ってから、一人で家に帰った。

Both are understandable because:

• は marks the topic
• で marks the location
• を marks the object
• に marks the destination

That said, not every order sounds equally natural in every context. The original sentence is very normal and easy to follow.

No. 見送る does not just mean to see with your eyes.

Here it means to see someone off—to go with them to the place they leave from and say goodbye as they depart.

So at an airport, 姉を見送る suggests something like:

• going with the older sister to the airport
• saying goodbye
• watching her leave

It is a very natural verb for this situation.

Because Japanese often omits information that is already understood.

After 友達は..., it is clear that the friend is still the subject of the later action unless something changes. So Japanese does not need to say 友達は again before 家に帰った.

This is one reason Japanese can sound compact: once the topic is established, it is often left unstated in the rest of the sentence.