DragonKing: Watanabe won it with 71 moves. The variation after the final move is as YuryShpilev points out. N-5c+ would be a magical sacrifice.
I've dealt with it in my blog at http://shogi-excitinggame.blogspot.com/
(hide) If you are waiting for your turn, click on "change" next to the "refresh" on the main page, then set refresh the page to 30 seconds to get your turn to move displayed faster. (Servant) (show all tips)