Starting the day sitting second, Katsuta leapt into an 11.4s rally lead over Hyundai's Esapekka Lappi after a drama-filled stage four, which resulted in Rovanpera and Ott Tanak retiring from the day's action.
Overnight leader and reigning world champion Rovanpera, making a return to the WRC in a part-time programme for Toyota, was the victim of a snowbank. His rival Tanak suffered a similar fate that damaged the radiator on his Hyundai.
