This song inspire me to do up a fic but what kind? I can't even think of any but how the song flows, a sad fic BUT ok, mental block.
This is what I can think, Impromptu one. I don't follow the lyrics. Based on what i think flows with the melody.

On that particular rainy day, 
You asked for a break-up.
We fought in the rain. The rain never seemed to stop.
No matter how loud I shouted at you to come back to me, it seemed my voice was drowned in the echo of the falling rain.
You turned your back against me.
"Please baby, give me another chance."

I waited outside her house in the rain.
Her bedroom light was on yet she did not come out to see me.
I stood like a fool, yet, I want to seek her forgiveness.
Please forgive me baby.
I shouted her name many times. All I got was nothing. No reply.
Is that the end of us? You know I love you very much.
I was wrong. The time you wanted a break-up, i did a lot of self-reflections.
I willing to change this time, for you.

I looked up. She slide open the window. She looked at me while I looked at her, hopefully she will forgive me.
Never did I expect, she threw all of the things I gave her all these while at me.
At that time, I knew her decision to break-up are final. I knew nothing more can be done to salvage our relationship.
I picked up the things I bought for her one by one.
Never knew if I cried, tears are washed out in the rain anyway.
Goodbye baby, as I left with a heavy heart.
I'll always love you.