Kristen Stewart said hi to fans when she arrived at the airport in Tokyo this morning. She's abroad to handle press for the final Twilight film, Breaking Dawn Part 2. While she's in Asia, her on-again boyfriend, Robert Pattinson, is in Sydney, where he attended a photocall and event with Twilight devotees this morning. Robert left LA just a few days ago, but Kristen stuck around to attend Katy Perry's birthday party. Kristen partied with friends like Katy's boyfriend, John Mayer, at the bash, held at the Magic Castle Friday night, ahead of Katy's actual 28th birthday Thursday.