Il narratore non è l'antagonista; semmai è un comprimario.

Italian usually uses the definite article more often than English. So il narratore means the narrator.

In many cases where English can omit an article, Italian still prefers one, especially with ordinary nouns used as clear roles or categories in a sentence.

• il narratore = the narrator
• l'antagonista = the antagonist
• un comprimario = a supporting character / secondary character

Because antagonista begins with a vowel, the article il becomes l' before it:

• il + antagonista → l'antagonista

This is called elision. It makes pronunciation smoother.

The same thing happens with many singular nouns:

• l'amico
• l'attore
• l'idea

Here semmai means something like:

• if anything
• rather
• at most
• if he is anything, he is...

So the sentence is not just saying he is not the antagonist. It adds a correction or a softer alternative:

• He isn’t the antagonist; if anything, he’s a supporting character.

In other contexts, semmai can also have other meanings, so it is a useful word to learn by context.

Because è is the verb essere in the third person singular: is.

• è = is

The accent is important because it distinguishes it from e, which means and.

Compare:

• è = is
• e = and

So:

• non è l'antagonista = is not the antagonist
• not non e l'antagonista, which would be incorrect

In Italian, simple negation is usually made by putting non before the verb.

• è = is
• non è = is not

Examples:

• È il protagonista. = He is the protagonist.
• Non è il protagonista. = He is not the protagonist.

So Il narratore non è l'antagonista is the normal Italian way to say The narrator is not the antagonist.

Because the sentence is making two slightly different kinds of statements.

• l'antagonista refers to a specific role: the antagonist
• un comprimario means a supporting character, one among that category

So the contrast is:

• he is not the antagonist
• he is, rather, a supporting character

This difference between definite and indefinite articles is very natural in both Italian and English.

Comprimario is a literary/theatrical term for a secondary or supporting character, not one of the main central roles.

Depending on context, it can mean:

• supporting character
• secondary character
• minor role

It is more specialized than a very common everyday word, so learners may not see it often outside literature, drama, film, or criticism.

Here it is masculine because it refers to a masculine role in the sentence, shown by the article l' and the overall context.

But antagonista is one of those nouns that can often have the same form for masculine and feminine, with the article showing the gender:

• l'antagonista = the antagonist (masculine or feminine, depending on context)
• un antagonista = a male antagonist
• una antagonista = a female antagonist

The same can happen with some profession or role nouns in Italian.

Because Italian, like English, often avoids repeating the subject when it is already clear.

After Il narratore non è l'antagonista, it is obvious that the second clause is still talking about the narrator, so Italian simply says:

• semmai è un comprimario

That is more natural and less repetitive.

The semicolon links two closely related clauses:

• Il narratore non è l'antagonista
• semmai è un comprimario

It shows a pause stronger than a comma, but not as final as a period. It fits well here because the second clause corrects or refines the first one.

You could think of it as:

• first: rejecting one role
• second: proposing a better description

Yes. A few natural alternatives are possible, though they may sound slightly different in tone:

• Il narratore non è l'antagonista; piuttosto è un comprimario.
• Il narratore non è l'antagonista, ma un comprimario.
• Il narratore, semmai, è un comprimario.

The original sentence is perfectly natural and gives a nuanced contrast. Semmai is especially good when the speaker wants to say if we had to label him, the better label would be...