The song is called '그리움에' in Korean which means 'In Longing/Yearning' and the English title is 'I will come to you' which are both mentioned in the chorus.
 

흰 눈이 내리던 날¹
너의 곁을 떠난 날
하루에도 수백 번씩
매일 끄적인 그 말

The day snow fell
The day I left your side
Hundreds of times in a single day,
Those words that I scribbled down

너무 그리워²
나를 안아줘

"I miss you"²
"Please hug me"

아름다운 기억에 잠겨
오늘도 웃으며 잠들길
따뜻한 봄바람 불 때쯤
너에게 너에게 갈게
약속해 너에게 갈게

Immersed in the beautiful memories
I hope you fall asleep smiling today too
When the warm spring wind blows
I'll go to you, to you
I promise that I'll go to you

추억도 그리움도
담긴 나의 그림
지나간 시간 속에
남은 단 하나의 색

Memories and longing both
Contained in my painting
Amid the time that passed by
Is only the color that was left

캄캄한 길 위에
한 줄기 빛 그대여

On that pitch-dark path,
You, who was a ray of light

아름다운 기억에 잠겨
오늘도 웃으며 잠들길
따뜻한 봄바람 불 때쯤
너에게 너에게 갈게
약속해 너에게 갈게

Immersed in the beautiful memories
I hope you fall asleep smiling today too
When the warm spring wind blows
I'll go to you, to you
I promise that I'll go to you

그리움에 잠시 떠나있어도
약속해 I will come to you
If you need me, I will come to you

Even if I'm away for a bit amongst this longing/yearning
I promise that I will come to you
If you need me, I will come to you

 

 

NOTES:
 

1. On the day Jin enlisted, it was snowing in Seoul and many other places in Korea.

2. The word used here for 'missing' (그리워) is closer to yearning or longing, which is a little bit stronger in tone than '보고 싶다' (I want to see you/I miss you).