Learn Hardcore Japanese: zyoyuutati no hyouzyou wo mite, watasi mo genki ni narimasita. - Seeing the actresses' expressions, I also felt better.

In Japanese, plural is often not explicitly marked, but たち can be added to people (and sometimes animals) to emphasize that there are multiple individuals.

So 女優たち means “the actresses” or “the group of actresses”, rather than just one actress.

What is the role of の in 女優たちの表情?

の here is the possessive/attributive particle, like “’s / of” in English.

女優たちの表情 literally = “the actresses’ expressions” or “the facial expressions of the actresses.”

Structure:

女優たち = actresses
の = ’s / of
表情 = facial expression(s)

So it’s saying the expressions that belong to / are shown by the actresses.

What exactly does 表情 (ひょうじょう) mean? Is it just “face”?

表情 does not mean “face” itself; it means “facial expression” or “the way one’s face looks as an expression of feeling.”

顔 (かお) = face (the physical face)
表情 (ひょうじょう) = facial expression, look on someone’s face
感情 (かんじょう) = emotion/feeling (inside, not necessarily shown)

So 女優たちの表情 focuses on how the actresses’ faces looked emotionally (smiling, lively, moved, etc.), not merely their physical faces.

Why is を used with 見て? What is 表情を見て doing grammatically?

を marks the direct object of the verb 見る (to look at / see).

表情を見て = “(having) looked at / seeing the expressions”

Breakdown:

表情 = expressions
を = direct object marker
見て = て-form of 見る

So 表情 is what is being seen. The phrase means that the speaker looked at the actresses’ expressions, and that action connects to what comes after.

What is the function of the て-form in 見て、私も元気になりました?

The て-form of a verb (here 見て) is often used to connect actions or clauses. In this sentence, it has a “and then / after / by doing X” nuance, often implying cause or sequence.

表情を見て、私も元気になりました。 can be understood as:

“After seeing the actresses’ expressions, I also felt better.”
“By seeing the actresses’ expressions, I also became cheerful.”
“When I saw the actresses’ expressions, I too became energized.”

So 見て connects the act of seeing with the resulting change of state (元気になりました). It suggests that seeing their expressions is the reason or trigger for becoming cheerful.

What does 私も mean here? Why is も used instead of は or が?

も means “also / too / as well.”

私 = I / me
私も = I also / me too

Using も implies there is some implicit comparison:

Maybe other people became cheerful as well.
Or maybe the actresses themselves were cheerful, and I also became cheerful by seeing them.
Or the context previously mentioned someone else’s feeling, and now the speaker says “I too…”

If it were 私は, it would just topic-mark “I” with no “also” nuance:

私は元気になりました。 = I became cheerful. (neutral)

With も:

私も元気になりました。 = I also became cheerful. (aligning the speaker with someone/something else)

Why is it 元気に and not 元気だ or 元気な before なりました?

元気 is a な-adjective (also acts like a noun). With なる (to become), な-adjectives usually take に to show a change of state:

元気になる = to become energetic / to feel better / to cheer up
きれいになる = to become pretty/clean
有名になる = to become famous

So:

元気に here is the adverbial/“to the state of 元気” form.
元気になりました = “(I) became 元気” → “I felt better,” “I became cheerful/lively.”

元気だ and 元気な are used differently:

元気だ。 = (I am) fine/energetic. (statement of current state)
元気な人。 = a healthy/energetic person. (modifying a noun)

With なる, you use に: 元気になる.

What does なりました mean exactly, and why is it in the ます-form?

なりました is:

なる (to become)
→ なり (連用形 / stem)
→ なりました (polite past: became)

So 元気になりました = “(I) became cheerful / I felt better / I got energized.”

It uses the ます-form (polite form) because:

The sentence is in polite style, appropriate for most everyday conversations with people you’re not very close to, or in writing.

Casual speech would use:

元気になった。 (same meaning, but plain/casual)

Who is the subject of 元気になりました? There’s no が or は in front of it.

The subject is understood to be 私 (I) from 私も earlier in the sentence.

Japanese often omits the subject when it is clear from context. The structure is:

(女優たちの表情を見て、)
私も　元気になりました。

So:

私も marks I as the person who “also” experienced the change.
元気になりました is what happened to that 私.

Even though there is no が, we know “I” is the one who became cheerful.

Could this sentence be phrased differently with the same meaning? For example, using なった or 見たら?

Yes. Some common alternatives (with their nuances):

女優たちの表情を見て、私も元気になった。
- Same structure, but plain past instead of polite.
- Natural among friends or in casual writing.
女優たちの表情を見たら、私も元気になりました。
- 見たら = “when I saw / if I see.”
- Slightly stronger sense of “when that happened, this (always) happens” or one-time sequence:
  “When I saw the actresses’ expressions, I (then) felt better.”
女優たちの表情を見て、元気になりました。
- Drops 私も.
- Still usually interpreted as “I became cheerful” from context, just without the “also” nuance.
女優たちの表情を見て、私も元気になったんです。
- Adds んです, which gives a more explanatory/“you see / it’s that…” tone.

All of these keep the same core idea:
Seeing the actresses’ facial expressions caused the speaker to become cheerful/energized.