That's a cap of Taeyang's cyworld and he used the N word as his nickname for his friend.
And to those who are wondering if Taeyang was the one who used the N word or if his friend was the one who used the N word, it's Taeyang.
The way cyworld works is, your nickname for your friend will appear right next to his/her name when he/she leaves a message at your cyworld.
source JFC, I knew that this day would come. SMH
Does this make him racist? imo No. But he is definitely ignorant and needs to be informed that shit like this isn't cool.