joyeoneun majimak mage deungjanghae.

조연 means a supporting role or supporting actor/character.

• 주연 = leading role, main actor
• 조연 = supporting role, supporting actor

In this sentence, it most naturally refers to the supporting character/actor who appears in the final act.

은 is the topic particle.

So 조연은 means something like:

• as for the supporting character
• the supporting character, ...

It marks 조연 as the thing the sentence is talking about. In English, we often do this just with word order and context, but Korean uses particles to show it clearly.

This can also give a slight contrastive feeling depending on context, like:

• The supporting character appears in the last act.
  (possibly implying someone else does not, or that we are specifically talking about the supporting character)

마지막 means last or final, and 막 means act in a play, musical, opera, or similar staged work.

So 마지막 막 means the final act or the last act.

This is a theater-related word. In other contexts, 막 can mean other things, but here it clearly means act.

In 마지막 막에, the particle 에 marks the place or point where something happens. Here it is best understood as:

• in the final act
• at the final act

With events in stories, performances, scenes, acts, and times, 에 is often used to show where or when something occurs.

So:

• 마지막 막에 등장해 = appears in the final act

등장해 comes from the dictionary form 등장하다.

• 등장 = appearance, entrance
• 하다 = to do

So 등장하다 literally means to make an appearance / to appear / to enter the scene.

The form changes like this:

• 등장하다 → 등장해

That is a very common contraction pattern for 하다 verbs in casual speech.

They are different speech levels or styles.

• 등장해 = casual, non-polite
• 등장해요 = polite
• 등장한다 = plain/written style, often used in narration, descriptions, essays, or formal storytelling

So the sentence you have is in a casual style. It might be used:

• in conversation with a friend
• in informal commentary
• in notes or casual narration

All three can express roughly the same basic meaning, but the tone is different.

Yes, it is a present-form verb, but in Korean this form can also describe something that happens in a story or plot summary.

So it can mean:

• appears
• shows up
• comes on stage

In plot summaries, Korean often uses the present form the way English also sometimes does:

• In the last act, the supporting character appears.

Usually it is very close to appear, but it has a slightly more specific feel of:

• making an appearance
• entering the scene
• coming on stage
• showing up in a work/story

It is especially common for:

• plays
• films
• novels
• characters
• public appearances

So in this sentence, 등장하다 fits very naturally because 막 already suggests a performance or dramatic work.

Yes. 막 can have several meanings in Korean, which can confuse learners.

For example, 막 can also mean:

• a curtain or screen
• a membrane
• in other expressions, something like just or recklessly, depending on usage

But here, because of 마지막 막 and the theatrical context, it clearly means act.

So in this sentence:

• 마지막 막 = the final act

Korean is basically a subject-object-verb language, and the verb normally comes at the end of the sentence.

So the order here is:

• 조연은 = as for the supporting character
• 마지막 막에 = in the final act
• 등장해 = appears

That final verb placement is one of the most important word-order differences from English.

Yes, Korean word order is more flexible than English because particles show each word’s role.

For example, you could also say:

• 마지막 막에 조연은 등장해.

This still means basically the same thing, but the emphasis may shift slightly. Putting 마지막 막에 first can highlight the setting first: In the final act, the supporting character appears.

The verb usually still stays at the end.

It can refer to either, depending on context:

• the supporting role
• the supporting actor
• the supporting character

In this sentence, since the verb is 등장해 (appears), it most naturally sounds like a supporting character or someone functioning as that character in the story/performance.

The sentence has a fairly straightforward, descriptive tone:

• As for the supporting character, they appear in the final act.

Because of the casual ending 등장해, it sounds informal rather than highly formal or textbook-like.

It feels like something you might say when:

• describing a plot
• talking about a play
• explaining when a character comes in
• casually discussing a performance