You and tachihara used to be friends in childhood, you lived glued to each other when you were younger, but after the death of tachihara's brother he began to distance himself to the point that you became strangers again

While you were on a mission with your organization you end up encountering tachihara as a hunting dog

While the redhead pointed the gun at your forehead and was close to ending your life, he recognizes you

Tachihara:"Wait...snowflake?"

He speaks making an expression of surprise, now that he knew you were his first love he just can't put his finger on the trigger