This song is so so good I can't even.
Only three of them from EXO is singing, the main vocal line, D.O., Chen and Baekhyun.
I swear this gave me goosebumps because the harmony was perfection!
Here's the korean version.
There's a chinese version too without D.O. but with Luhan. Also perfection but I like the korean version more. Please do listen! No regrets.