asita ha tomodati to issyo ni umi no syasin wo tori ni ikimasu.

明日は makes tomorrow the topic of the sentence.

So the sentence is framed as As for tomorrow, ... or Tomorrow, ...

In Japanese, time expressions like 明日 can appear without a particle, but adding は gives it more of a topic/contrast feeling. It can sound like:

• Tomorrow, I’m going...
• As for tomorrow, I’m going...

So:

• 明日、友達と一緒に海の写真を撮りに行きます。 = neutral Tomorrow, I’m going...
• 明日は、友達と一緒に海の写真を撮りに行きます。 = Tomorrow (as opposed to some other day), I’m going...

They are related, but they do slightly different jobs.

• 友達と = with a friend / together with a friend
• 一緒に = together

So 友達と一緒に is literally something like together with a friend.

In many cases, 友達と by itself is enough:

• 友達と行きます。 = I’m going with a friend.

Adding 一緒に emphasizes the idea of doing it together:

• 友達と一緒に行きます。 = I’m going together with a friend.

It is very natural to use both.

一緒 means together / the same company / being together.

When used adverbially to describe how an action is done, it often takes に:

• 一緒に食べる = eat together
• 一緒に行く = go together

So in this sentence, 一緒に tells you how the action happens: they are going together.

Here, の connects two nouns.

• 海 = sea
• 写真 = photo
• 海の写真 = photo(s) of the sea

A very common use of の is like English of or a possessive-style connector.

Examples:

• 日本の車 = Japanese cars / cars of Japan
• 猫の写真 = a photo of a cat
• 海の写真 = a photo of the sea

So 海の写真を撮る means to take pictures of the sea.

Usually, 海の写真 most naturally means photos of the sea.

If you wanted to stress at the sea/beach, Japanese would more naturally use something like:

• 海で写真を撮る = take pictures at the sea/beach

So the difference is:

• 海の写真を撮る = take pictures of the sea
• 海で写真を撮る = take pictures at the sea

In your sentence, the focus is on the subject of the photos: the sea.

This is a very important grammar pattern:

verb stem + に + 行く = go in order to do ...

The dictionary form is:

• 撮る = to take (a photo)

But before に行く, Japanese uses the verb stem (often called the masu-stem):

• 撮る → 撮り
• 撮ります comes from this stem too

So:

• 撮りに行きます = go to take pictures

Not:

• 撮るに行きます ❌

More examples:

• 食べに行きます = go to eat
• 見に行きます = go to see/watch
• 買いに行きます = go to buy

No. 撮り is not the て-form.

For 撮る:

• dictionary form: 撮る
• masu-form: 撮ります
• stem / masu-stem: 撮り
• て-form: 撮って

In this sentence, the form used is the stem:

• 撮りに行きます

The て-form would be used in other patterns, such as:

• 写真を撮って、帰ります。 = I take pictures and go home.

It is the pattern:

verb stem + に + 行く = go to do something = go in order to do something

So here:

• 写真を撮りに行きます
• literally: go for taking photos
• natural English: go to take photos

This pattern expresses purpose.

You can also use it with 来る:

• 勉強しに来ました。 = I came to study.

Because Japanese sentences normally put the main verb at the end.

The main action here is 行きます = go.

Everything before it gives extra information:

• 明日は = as for tomorrow
• 友達と一緒に = together with a friend
• 海の写真を = photos of the sea
• 撮りに = in order to take

Then finally:

• 行きます = go

This is very typical Japanese word order: details first, main verb last.

を marks the direct object of the verb.

Here, the object is:

• 海の写真 = photos of the sea

And the verb is:

• 撮る = to take (a photo)

So:

• 海の写真を撮る = take pictures of the sea

Even though the sentence continues with に行きます, the を still belongs to 撮り:

• [海の写真を撮り] に行きます
• go [to take photos of the sea]

By itself, 友達 can mean friend or friends, depending on context.

In this sentence, many learners will translate it as with a friend, but Japanese does not always force you to mark singular vs. plural as clearly as English does.

So depending on context, it could mean:

• with a friend
• with friends

If the speaker wanted to be very clear, they could say something like:

• 一人の友達 = one friend
• 友達たち = friends

But in everyday Japanese, just 友達 is very common.

Yes, absolutely.

You could say:

• 明日は友達と海の写真を撮りに行きます。

This is still natural and correct.

Adding 一緒に just makes the together feeling more explicit:

• 友達と行きます = go with a friend
• 友達と一緒に行きます = go together with a friend

So 一緒に is not required, but it is natural.

Yes.

Both are natural:

• 明日、友達と一緒に海の写真を撮りに行きます。
• 明日は、友達と一緒に海の写真を撮りに行きます。

The version with は gives a little more topic or contrast nuance. The version without it is often a bit more straightforward.

So the difference is not about correctness; it is more about nuance.

A natural reading is:

• 明日 → あした
• は → pronounced わ
• 友達 → ともだち
• と → と
• 一緒 → いっしょ
• に → に
• 海 → うみ
• の → の
• 写真 → しゃしん
• を → pronounced お
• 撮り → とり
• に → に
• 行きます → いきます

So the full sentence is read:

あした は ともだち と いっしょ に うみ の しゃしん を とり に いきます。

Those spaces are usually just for learners.

Normal Japanese writing does not usually put spaces between words like this:

• 明日は友達と一緒に海の写真を撮りに行きます。

Learning materials often add spaces to make the structure easier to see. So the spaced version is a study aid, not standard native formatting.