5. Forever Yours (feat. Soyou)
One of Key's first solo releases, "Forever Yours," has a light, tropical-house sound perfect for summer. Featuring Soyou (formerly of SISTAR), the track talks about unwavering love, and the breezy production makes it a standout in Key's discography. It’s an easy-going, feel-good song that shows Key’s ability to explore diverse genres while maintaining his signature flair.