The song is kids again by nightcore switching vocals

Natsu

I know a girl who likes to drink her coffee black
Natsu said smirking at Kasai
Cause sugar, no, she don't got time for that
Leaves her desires at the welcome mat when she walks in

Kasai

Yeah, I know a boy who likes to keep his burner on
Kasai said smirking
He's always running with no one to keep warm
It's like he's flirting with the smoke alarm, his fire's fading

Together

But still we laugh, we cry, we fall, we get high
Just like we were kids, just like we were kids
And when I, I'm feeling small you get me through it all
Just like we were kids, just like we were kids again

Natsu

I know a girl who's never tried to settle down
She wears her loneliness like a crown
But when she smiles all the kings will bow down, down, down

Kasai

And I know a boy who's broken every vow he's made
Who's spoken every capped phrase
But he can listen like a rainy day and drown it out
Kasai said smiling softly

Together

But still we laugh, we cry, we fall, we get high
Just like we were kids, just like we were kids
And when I, I'm feeling small you get me through it all
Just like we were kids, just like we were kids again

Just like we were kids, just like we were kids again
Just like we were kids
Just like we were kids, just like we were kids again

Kasai

So we laugh, we cry, we fall, we get high
Just like we were kids, just like we were kids

Natsu

And when I, I'm feeling small you get me through it all
Just like we were kids, just like we were kids again

Together

But still we laugh, we cry, we fall, we get high
Just like we were kids, just like we were kids
And when I, I'm feeling small you get me through it all
Just like we were kids, just like we were kids again

Just like we were kids, just like we were kids again
Just like we were kids
Just like we were kids, just like we were kids again

Just like we were kids, just like we were kids again
Just like we were kids
Just like we were kids, just like we were kids again

♡ Natsu... Have we ever grown up?♡
Kasai said laughing.
♡ No, never♡ Natsu replied.