KOOL is an utaite who began uploading covers in 2009. He usually sings VOCALOID songs, as well as songs from some rock groups, such as Acid Black Cherry and UVERworld;
Unsurprisingly, he usually chooses to cover songs of the rock genre, which suits his rather rough and strong voice.
He can also scream and will sometimes cover songs with an unexpected screamo rock arrange, such as his rock arrange cover of "PONPONPON". However, when he uses less power, such as in his cover of "from Y to Y", his voice still maintains its rough quality, and is said to have a calming effect.
His first uploaded cover was of "from Y to Y", which had unexpectedly high quality for a first upload. Later on, many were surprised at his ability to shout and hit high notes, which did not reflect their impression from the first few uploads. His most popular cover is his retake of "Bye-bee Baby Sayounara", which has over 67K views and over 3K Mylists as of June 2013.
As his name would suggest, his fans often describe his voice as very "cool." However, his name also stands for Keep On Our Lifestyle, which can been seen in his logo.
He is often portrayed with mid-length dark brown hair and blonde bangs, which was previously his actual hairstyle.
He is good friends with un:c, as they interact often on Twitter and have appeared in several live concerts together.
On September 10, 2016, he started using the name GORYU (吾龍) as the vocal of rock band DOPEDOWN and became professional singers.