minna de moriagarou.

みんなで means everyone together or all of us together.

The particle で is important here. It marks the group as the people doing the action together as one group. So this is not just みんな = everyone; it is specifically with everyone / all together.

A natural way to think of it is:

• みんな = everyone
• みんなで = all together / together with everyone

In this sentence, it sets up the feeling of let's all get into it together.

Here, で shows the group involved in doing something together.

This use of で is common in Japanese:

• 家族で旅行する = travel with the family
• 二人で話す = talk together, as two people
• みんなで歌う = sing all together

So in みんなで盛り上がろう, the で does not mean location, as it often does in other sentences. Instead, it means something like as a group or together.

盛り上がろう is the volitional form of 盛り上がる.

The volitional form is often used to mean:

• let's ...
• shall we ...
• sometimes a strong come on, let's ...

So:

• 盛り上がる = to get excited / to liven up / to have the mood build
• 盛り上がろう = let's get excited / let's get fired up / let's make this lively

This form sounds like an invitation or encouragement.

盛り上がる is a u-verb.

To make the volitional form of a u-verb, you change the final u sound to the o row and add う:

• 上がる → 上がろう
• 話す → 話そう
• 行く → 行こう

So:

• 盛り上がる
• becomes 盛り上がろう

That is why it ends in ろう.

Originally, 盛り上がる can literally mean something like to swell up or to rise up. But in everyday Japanese, it is very often used figuratively.

In this sentence, it means things like:

• to get excited
• to get into the mood
• to liven things up
• to have a good energetic atmosphere

So みんなで盛り上がろう is not about something physically rising. It is about the mood, energy, or excitement building among everyone.

This is a very good question, because the two are related but different.

• 盛り上がる = to get excited / for the atmosphere to become lively
  
  • usually treated as intransitive
• 盛り上げる = to liven something up / to get people excited
  
  • usually treated as transitive

So:

• みんなで盛り上がろう = Let's all get excited together
• 場を盛り上げよう = Let's liven up the atmosphere
• イベントを盛り上げよう = Let's make the event exciting

With 盛り上がろう, the focus is on everyone entering an excited, lively mood together.
With 盛り上げよう, the focus is more on actively making something lively.

It is casual.

The volitional form 〜よう is often used in casual speech:

• 盛り上がろう = casual Let's get excited
• 盛り上がりましょう = polite Let's get excited

So a more polite version would be:

• みんなで盛り上がりましょう。

The original sentence sounds friendly, energetic, and natural in informal situations such as with friends, classmates, teammates, or an audience.

In this sentence, みんな normally includes the speaker and the people being addressed: all of us / everyone here.

Because the sentence is 盛り上がろう = let's get excited, the speaker is naturally inviting others to join in together. So the feeling is:

• Come on, everyone, let's get into it together

Depending on context, みんな could refer to a specific group such as:

• everyone at the party
• everyone in the class
• everyone on the team
• the audience

Japanese often leaves that context unstated if it is already obvious.

Yes. It can be written as 皆.

So you may see:

• みんなで盛り上がろう。
• 皆で盛り上がろう。

Both are fine. In everyday writing, みんな in hiragana is very common because it feels friendly and easy to read.

Those spaces are probably just there for learning purposes.

In normal Japanese writing, you would usually write it without spaces:

• みんなで盛り上がろう。

Japanese does not normally separate words with spaces the way English does. Textbooks and beginner materials sometimes add spaces to make the sentence structure easier to see.

Yes. Even if the basic meaning is already known, there are several natural English renderings depending on tone and situation:

• Let’s all have fun together.
• Let’s all get excited.
• Let’s get fired up together.
• Let’s make this lively, everyone.
• Come on, everyone, let’s get into it.

The exact best translation depends on context. For example:

• at a concert or event: Let’s get fired up together!
• at a party: Let’s all have fun!
• in a classroom or group activity: Let’s all get into it together!

Yes, you could say just 盛り上がろう, and it would still sound natural.

• 盛り上がろう。 = Let’s get excited / Let’s get into it.
• みんなで盛り上がろう。 = Let’s all get excited together.

Adding みんなで makes the sentence more explicitly group-focused. It emphasizes that this is something everyone should do together, not just a general suggestion to be enthusiastic.