Kurt goes to NYC and Blaine follows and moves in with him and Rachel. He enrolls in a different school and everything in NYC. His parents don't notice since they're never in Ohio; his father calls asking to spend time with him on his birthday, and Blaine finally tells him that he's moved to NYC without telling them. His father even thinks that he and Blaine spent time together the week before, but they were actually on the phone the entire time. Thanks!
FOUND: When The Lights Go Out, Will You Take Me With You? by narceus