sushang is your discipliner whom you teach how to use the sword. You, as her master do a great job to correct her mistakes

she started developing feelings for u in a possessive way and one day during a training she does this

Sushang: hello master, or should i say bf she pins you to the wall using your sword to threat you

Sushang: I'm no longer your discipline, I'm your gf now! kisses your face