sekkaku tomodati to issyo ni eigakan ni kitanoni, eiga ha sukosi taikutu desita.

せっかく adds the feeling of going to special effort or finally having a good chance to do something.

In this sentence, it suggests something like:

• we came all this way
• we made the effort to come
• it was a nice opportunity

So the speaker is not just saying we came to the movie theater. They are saying there was some value or effort in doing so, which makes the disappointing result stand out more.

A very common pattern is:

• せっかく ～ のに = even though ~ / after going to the trouble of ~, unfortunately ...

So せっかく helps create the feeling of what a shame.

のに shows contrast or disappointment. It often means:

• even though
• although
• despite the fact that

In this sentence:

• 来たのに = even though we came
• then the disappointing result is: 映画は少し退屈でした = the movie was a little boring

So the full emotional flow is:

• We made the effort to come to the theater together, but...
• the movie was a little boring.

With せっかく, のに often sounds especially regretful or disappointed.

All three can connect clauses, but they have different nuances.

• 来て simply links actions: came, and...
• 来たけど means came, but... and is fairly neutral
• 来たのに means even though we came... and strongly suggests disappointment, surprise, or frustration

So:

• 来たけど = a plain contrast
• 来たのに = a contrast with emotional weight

Because the sentence is expressing regret/disappointment, のに fits very well.

It is in the past tense because the action of coming to the movie theater happened before the judgment about the movie.

The sequence is:

1. We came to the theater.
2. We watched the movie.
3. The movie turned out to be a little boring.

So 来たのに means even though we came or after coming.

Japanese often uses the past form before のに when talking about something that already happened and led to a disappointing result.

They are doing different jobs.

• 一緒に: the に goes with 一緒 and makes it into an adverb-like expression meaning together
• 映画館に: this に marks the destination, meaning to the movie theater

So:

• 友達と一緒に = together with a friend / with friends
• 映画館に来た = came to the movie theater

Even though both are に, they are unrelated grammatically.

Yes, sometimes one can be enough, but using both is very common and natural.

• 友達と来た = came with a friend / came with friends
• 友達と一緒に来た = also came together with a friend / friends, but it emphasizes the togetherness a little more

So 一緒に is not required, but it adds a bit of warmth or clarity.

You can think of it like:

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

Putting them together is perfectly normal in Japanese.

Using は makes the movie the topic and often helps create contrast or evaluation.

Here, the speaker is basically saying:

• As for the movie, it was a little boring.

That works well because the first part talks about the outing:

• we came to the theater together

Then the second part shifts focus to the movie itself:

• the movie, though, was a little boring

If you used 映画が, it would sound more like simply identifying the subject. 映画は feels more natural here because the speaker is commenting on it as a topic and contrasting it with the positive expectation created by せっかく.

Both are grammatically correct. The difference is mainly politeness.

• 退屈でした = polite
• 退屈だった = plain/casual

Since the sentence uses polite style overall, でした matches that style.

Also, 退屈 is a na-adjective / adjectival noun, so in the past tense it becomes:

• plain: 退屈だった
• polite: 退屈でした

退屈 is a na-adjective type word.

That means:

• present plain: 退屈だ
• present polite: 退屈です
• past plain: 退屈だった
• past polite: 退屈でした

When it directly modifies a noun, it takes な:

• 退屈な映画 = a boring movie

In this sentence, it is used at the end as a predicate:

• 映画は少し退屈でした = the movie was a little boring

Yes, 少し literally means a little, but in a sentence like this it often softens the statement.

So 少し退屈でした can mean:

• was a little boring
• was kind of boring
• was somewhat boring

It makes the comment less harsh than just saying:

• 映画は退屈でした = the movie was boring

Japanese often uses words like 少し to sound less direct or less blunt.

It can mean a friend or friends. Japanese nouns usually do not show singular vs. plural unless the context makes it clear.

So 友達と一緒に could mean:

• together with a friend
• together with friends

Both are possible from the Japanese alone. The exact number would come from context.

Yes, very likely.

Japanese often leaves out subjects when they are obvious from context. In this sentence, the speaker probably means something like:

• I came to the movie theater with my friend, but the movie was a little boring or
• We came to the movie theater together, but the movie was a little boring

Japanese does not need to state I or we if the listener can understand it already.

So omission here is completely natural.

Yes, very much.

This pattern often carries feelings like:

• disappointment
• regret
• frustration
• what a waste
• what a shame

In this sentence, the feeling is something like:

• We came all the way here together, and yet the movie was boring.

So even if the basic meaning is already clear, a learner should notice that the sentence is not emotionally neutral. It carries a sense of letdown.