My wa guess - they kill each other. The Samurai makes a lightning fast downward diagonal slashing blow aimed at the European swordsman's neck / shoulder area. The European makes an equally lightning fast thrust towards the Samurai's heart. The thrust has a slightly shorter distance to go, so the thrust goes home first. However, the Samurai has by that time generated enough momentum to carry the slash home and decapitate the European. That's how I saw it go down anyway.
