I read only through the first 7 pages, so this may have been mentioned already, but in the 1954 film, Seven Samurai there are several scenes with a kamisori. One where a samurai has his head shaved, and another a peasant cuts his daughters hair with the razor. Very cool film, and I can't wait to see the remake, 13 Assassins!
-Matt-
13 Assassins is absolutely awesome! But although it has several similarities and some characters inspired by Seven Samurai, it is not a remake of Seven Samurai.