Kerry isn't a character who'll cross your path unless you really explore the Side Jobs involving Rogue and Johnny. Eventually, you'll be tasked with breaking into his house to see if you're okay, and eventually trying to get the Samurai band back together for one last gig. But, after these missions, Kerry will call asking for your help, triggering a secondary string of missions that will both conclude his mission arc for the associated achievement, and open up a romance option with him.
It all involves issues and problems involving Kerry's solo career, and initially about a Japanese pop band called Us Cracks doing a cover of one of his songs. But, later on it's about getting to the bottom of what's really holding Kerry back.