So, apparently my 3 favorite K-groups (Beast/Highlight, BTS, and CNBlue) have song with youth theme. I love each version, but this one from highlight (or beast back then) has more cheerful vibe. Here is the lyrics translated in english (originally on japanese language). I personally love the music video too, although it's just simply showing their rehearsal and performance on stage. Go check it on youtube if it's still available (because the original one from Beast Music youtube channel is no longer available).

Album : STAY FOREVER YOUNG

Genre : J-Pop

Release Date : 2015.12.25

Translation

The scenery of this town we used to look at,

those days when we child,

Do you remember it?

LETS STAY FOREVER YOUNG

In this mess, let’s look at the seven colors of the world

I remember the future we have painted

WE STAY FOREVER YOUNG

There’s only hope that goes on

It will certainly be a drama here

Wherever we are, we’ll change

Oh Oh… It’s sparkling

STAY FOREVER YOUNG

With happiness, I’m full of overflowing heartbeats

Oh Oh.. TOGETHER WE ARE ONE

STAY FOREVER YOUNG

Oh Oh… It’s sparkling

STAY FOREVER YOUNG

I’ll always be a kidult (childish)

In this society, how can we manage to have an endless existence ?

Clock’s hands are fast or slow,

I don’t forget those feelings of that day

I want to bring together my memories’ fragments

What is the “me” of today looking at ?

Wanna go back down to my memories road

Life is like a roller coaster

No one can predict anything

Feelings are accelerating

LETS STAY FOREVER YOUNG

STAY FOREVER YOUNG

Raising your head to admire the sky,

Look at each dream that you find here

Oh Oh… It’s sparkling

STAY FOREVER YOUNG

THROW YOUR HANDS UP HIGH

Oh Oh.. TOGETHER WE ARE ONE

STAY FOREVER YOUNG

The sun which will never go down

I want to believe it

The limit of the dreams we see

Wherever we are, we’ll still change

Oh Oh… It’s sparkling

STAY FOREVER YOUNG

With happiness, I’m full of overflowing heartbeats

Oh Oh.. TOGETHER WE ARE ONE

STAY FOREVER YOUNG