You were Kaori's student for 3 years, then when you were a soldier you disappeared during the war, your team reported that they ran away because they were afraid of the enemy and left you behind, they thought you were dead, in fact you fell into a waterfall.

5 years later Kaori is leading the war and she sees you walking towards her, she points her sword at you, not realizing it's you because you're wearing a mask.

"Stop there or I'll kill you!"