Help me!! Help me!!

You’re really going to leave me all alone like this?

〜わけ? gives the question an incredulous "how can that be?" feeling.

If you’re going to keep making me feel this lonely...

させ続ける means continuing to make someone do or feel something.

I’ll go flying off somewhere far away.

〜てしまう adds finality: ending up going far away.

Hey. Is that really okay with you?

いいの? is a short direct challenge: "is that okay?"

Help me, please, I can’t take more of this...

お願い is a standard plea word, often equivalent to "please" or "I beg you."

I can’t put up with this anymore. (Ha) (Ha) (Ha)

なんて is dismissive here: "things like endurance..."

Just endlessly waiting, endlessly waiting...

〜だけの means merely or only. Repeating the line makes the waiting itself feel monotonous.

A pitiful waiting girl.

待つ子ミジメックス is a comic coined phrase built from 待つ and 惨め.

Shinagawa, Gotanda... (Ah)

The place-name listing gives the song a restless searching rhythm.

Azabu, Roppongi...

These are well-known city/nightlife areas, so the place names imply going out and social activity.

Shinjuku, Shin-Okubo... (Ah)

Another short place-name roll call, used more for rhythm and search-energy than for description.

Where are you out having fun?

遊んでる is casual speech for being out having fun or hanging out.

Even though inside I’m always screaming...

いっつも is a highly spoken version of いつも.

...in front of him I end up pretending I understand.

フリする means pretending. しちゃう is colloquial してしまう.

Just dreaming is easy.

だけじゃ means "just ... is not enough / if it's only..."

Answer me with your whole body.

全身で literally means with the whole body.

Empty promises? No thank you.

口約束 means a merely verbal promise. The English phrase works as a punchline.

Make this a place that’s easy to live in for me.

The special reading 国(とこ) is stylized. It makes "country" sound more like "place" while keeping the larger written image.

A sparkling girl.

キラキラしてる means sparkling or shining in an ongoing way.

I’m going to spread my wings.

羽ばたく means spreading wings or taking flight.

A wishy-washy boy.

グズグズ means sluggish, indecisive, or dragging things out.

Don’t regret it later.

〜しないでね is a soft warning/request: "don't..."

Out of a crisis...

ピンチ is the common loanword for pinch, crisis, or tight spot.

...I’ll seize glory.

掴みとる means seizing or grabbing and taking for oneself.

Help me, please, fragile little me...

か弱い means delicate or frail. It is a somewhat stylized self-description.

It doesn’t even feel like tears will come. (Ha) (Ha) (Ha)

〜そうにない means it does not seem likely that something will happen.

I can’t say what I really feel, I can’t say what I really feel.

本音 means one's true feelings, as opposed to a socially managed front.

A can’t-say-it Nightingale. (Ah) (Ah Uh)

言えナイチンゲール is a pun combining 言えない with "Nightingale."

Osaka, Nagoya... (Ah Ah Ah)

The place-name sequence widens beyond Tokyo, which makes the search feel exaggerated.

Sapporo, Hakata... (Ah Uh)

Again the place names are functioning as chant rhythm as much as geography.

Hiroshima, Sendai... (Ah Uh)

Another example of place names being used for escalation and rhythm.

Are you even in Japan?

A comic exaggeration: maybe he is not even in Japan.

If you were kind to me, I feel like I’d burst into tears.

優しくされたら is passive: if someone treated me kindly.

What exactly is the basis for his cocky confidence?

どこにあんの is compressed spoken Japanese for どこにあるの.

If I give up, I’ll be admitting defeat.

Both verbs use colloquial 〜ちゃう, which keeps the line spoken and forceful.

That much, at least, I can’t do.

A plain sentence shape, but the topic marker は makes the refusal focused: that much, at least, no.

I won’t let loneliness swallow me whole.

飲みこまれる means being swallowed up or engulfed.

This is exactly the moment to hold firm.

踏ん張りどころ is a useful everyday phrase for the key moment when you have to hold firm.

A sparkling girl, I’m going to spread my wings; a wishy-washy boy, don’t regret it later.

The refrain is repeated in one compressed block here instead of being broken into separate lines.

Reality that can even be learned from criticism.

アンチ is the loanword for haters, critics, or people against you.

A sparkling girl, I’m going to spread my wings; a wishy-washy boy, don’t regret it later.

The repeated refrain wording stays the same, but by this point it functions more like a slogan.

From a crisis, I’ll seize glory.

栄光 means glory. It is deliberately larger-than-life wording.