Entire video was mostly black and white,
Basically, it was a song and music video about a couple in a dark world where it rains all the time.
A guy and a girl
I think and the girl is carrying a parasol (I think it's red?)

The animation then went with them climbing up the tower
Finding a door
And opening it where they found light and discovered flowers just waiting on the other

Does anyone know what I am talking about here?
It's a pretty old song. Like decades old and I think it's original was a vocaloid song

Please help. I wish to listen to it again