I hear this every morning at least a couple time because they loop it in the study pit (aka the family restaurant where I do lots of homework). They have also been playing it in the street in Shibuya. I could never really catch the words, though, so I decided to investigate....
Beware, lol:
Marshmallow Day - Mr. Children
Like a race car engine,
my heart is rumbling
This feeling well up towards my center
You're beautiful
It's marshmallow day
Just like a 3D movie
A smile straight out of Hollywood
I lose myself
as I'm gradually captivated
Don't go disappearing
like the taste of chewing gum
We're blowing sweet memory bubbles
Carefully, then crazily
I want to savor your texture
Everything is a taste of you
Even though I know there are other things I really should be doing
I can't concentrate
Like bells ringing on high
You're beautiful
Echoing
Although we've been getting along just fine lately
wanting for nothing
I imagine of a world without you
and I'm terrified
Even if I can't get enough sleep
If I can see you, I'll come with bells on
I'm longing for that moment
I'll match your key
Let's hum the same song
Everyday I sing for you
My heart soars
when I touch the gentle warmth of your body
Ah, I'm so happy
I could die
Buried in your sighs
and this sweet mood
Don't go disappearing
like the taste of chewing gum
We're still blowing sweet memory bubbles
Carefully, then affectionately
I want to savor your texture
Everything is a taste of you
I'm gonna match your key
Let's sing a happy song
Everyday I sing for…
Everything is a taste of…
Everyday, marshmallow day
WHAT DOES IT MEAN? Proooobably nothing, but ok, pretty catchy. You listened twice, didn't you!