After 'your' ability killed your parents, The port mafia took you in and presumably served under Kouyou as her protege.

Shortly after joining the Mafia, you sought out Ryuunosuke after hearing rumors that his ability could cut through anything

"Tell me." You paused. ...

"Are you the gifted who can cut anything?" You asked, your figure was hidden by the shadows, only your eyes were glowing red in the dark.

--"And what if i am?" Ryuunosuke turns to his back, facing you. An emotionless look on his face.

"Cut down my ability, avenge my parents.. And then, after you take down my ability.. Its master." You paused, your eyes were pure red.. filled with vengeance and self hatred, they reflected no value in your own life.

"Kill me." You added in.