tomodati ha senkou, watasi ha koukou da.

Yes. 先攻（せんこう） means going first or taking the first turn, and 後攻（こうこう） means going second or taking the second turn.

These are especially common in:

• games
• sports
• matches
• card games
• any situation where turn order matters

So this sentence sounds very natural in a game or match context.

The two は particles mark a contrast:

• 友達は先攻
• 私は後攻だ

This gives the sense of as for my friend..., as for me... or my friend goes first, while I go second.

Using は twice is very common when comparing or contrasting two things. Here, it clearly sets up the two roles against each other.

You could imagine が in some contexts, but は is the natural choice here because the sentence is contrasting two people’s roles.

• は = topic / contrast
• が = identifies or emphasizes the subject

Here the speaker is not mainly answering who goes first? in a neutral identifying way. Instead, they are laying out a contrast:

• Friend: first
• Me: second

So は fits much better.

Both are possible.

• 友達は先攻、私は後攻だ。
• 友達は先攻だ、私は後攻だ。

In Japanese, when two parallel phrases are put side by side, the first だ is often omitted because it would sound a little repetitive. The final だ is enough to complete the sentence.

So the given sentence is natural and efficient. It is a very common pattern in Japanese.

Yes, in casual speech it often can:

• 友達は先攻、私は後攻。

That sounds casual but natural, especially in conversation.

However:

• 友達は先攻、私は後攻だ。 = plain declarative style
• 友達は先攻、私は後攻です。 = polite style
• 友達は先攻、私は後攻。 = casual / clipped style

Yes, 私 could be omitted if the context is already clear.

For example, if you are obviously talking about yourself and your friend, you might hear:

• 友達は先攻、後攻は私。
• 友達は先攻で、私は後攻。
• or simply a different phrasing depending on context

But in the original sentence, 私 is included to make the contrast very clear and balanced:

• 友達は ...
• 私は ...

That symmetry sounds neat and natural.

The readings are:

• 友達 → ともだち
• は → pronounced wa here
• 先攻 → せんこう
• 私 → わたし
• 後攻 → こうこう
• だ → da

So the full sentence is read:

ともだちは せんこう、わたしは こうこう だ。

This is one of the most important beginner points in Japanese.

The particle は is normally read ha when it is part of a word, but when it is used as the topic particle, it is pronounced wa.

So here:

• 友達は = ともだちは but pronounced ともだちわ
• 私は = わたしは but pronounced わたしわ

The spelling stays は, but the pronunciation changes because it is functioning as a particle.

Historically, the kanji suggest something like attacking first and attacking later, but in modern usage these words usually mean the first player/side and the second player/side in a match or game.

So you should usually understand them functionally as:

• 先攻 = first turn / first side
• 後攻 = second turn / second side

You do not need to imagine literal attacking every time.

Yes. That is also natural:

• 友達が先攻で、私は後攻だ。
• 友達は先攻で、私は後攻だ。

Using で connects the two parts more explicitly, similar to and or a linking form.

The original sentence with the comma is also natural and slightly more compact:

• 友達は先攻、私は後攻だ。

Both are fine; the nuance is mostly about style and flow.

Yes. In Japanese, possession is often left unstated when it is obvious from context.

So 友達 here naturally means my friend in English, even though Japanese does not explicitly say 私の友達.

If needed, the speaker could say:

• 私の友達は先攻、私は後攻だ。

But that is usually unnecessary if the relationship is already clear.

Not necessarily. だ is the plain form of the copula and can be used by any gender. However, in actual speech, sentence-final だ can sound more direct or blunt, and that may sometimes feel more masculine depending on the speaker and situation.

In careful or neutral speech, many speakers would say:

• 友達は先攻、私は後攻です。

So:

• だ = plain, direct
• です = polite

The grammar itself is not exclusively masculine.

Yes, if you are talking about a game, match, or turn order. It is short and natural.

Depending on the situation, people might also say:

• 友達が先で、私は後。
• 友達が先攻で、私は後攻。
• 友達は先攻、私は後攻です。

The original sentence is perfectly natural, especially as a straightforward statement of roles in a game.