The audio is Junsu singing a cover of Fox Rain’ from My Girlfriend is a Nine-Tailed Fox OST.
It is originally sung by Lee Sun Hee. Near the end of the video is a past quote from Junsu:

[TRANS]
‘Happiness’ is more than dreaming about what I cannot have. I think I will obtain it by appreciating what I am having at the moment. No matter if there is only 1 or 100 of the fans who make me happy, even if there is only one stage for me, I will still do my best and show a good performance. If there are still people who love my music, like waves, like winds, I will fly to wherever that is and sing. Today. I am happy that I am able to be with everyone who is here to tell me they are happy because of me. Thank you very much and I love you.
(Cr. XIA_baby via XIA_world)

Translation of lyrics to ‘Fox Rain’:

I still don’t understand love
So I can’t get any closer
But why does my foolish heart
keep pounding?

I’m haunted by you again and again
I just can’t get away
This hopeless love
Hurts my heart so much

Going from day to night
You’re all I think about
Being so pitiful and silly
What should I do?

The heart follows love
What am I going to do?
This hopeless love
Hurts my heart so much

Dubirubiruraffa
Dubirubiruraffa
Dubirubiru dubirubiru
dubirubiruraffa

Dubirubiruraffa
Dubirubiruraffa
Dubirubiru dubirubiru…~

Going from day to night
You’re all I think about
Being so pitiful and silly
What should I do?

The day when my pain fades away
Will that day ever come?
Being so pitiful and silly
What can I do after all?

The moonlight is so beautiful
I just can’t get away
Let me lie down by your side for a moment
A moment, just a moment

[x8]
Dubirubiruraffa
Dubirubiruraffa
Dubirubiru dubirubiru
dubirubiruraffa..~

Video Credit: XIA DAY
Lyrics Credit: tryp96 + airendrama@youtube via eklyricos
Shared By: JYJ3 + miaw0730