One shot, One kill

Sayuri Koixaizumi S. Dixon is the 16 year old daughter of William Dixon and Sayaka Dixon, leaders of the underground Mafia Group, Black Bullets. At the ripe age of 7, she had learned how to shoot a sniper. And at the age of 9, she had her very first kill. Everything was perfect until her father was killed right in front of her. She swore on her father's name that she will kill the culprit to her father's name. After his father's death, everything in the mafia went downhill. She had to step up to the position as the Black Bullet's mafia throne. She meets leader of the other underground mafia, Red Blade and his father's friend's son, Sirius Draco D. Gray. He offers her help to find the culprit since he also needed her help to find the culprut of his mother's death. She accepts it and they help each other. They surprised each other with the tension of trying to find the culprit. As they lower the tension, they fall for each other. Will they keep their guards up in case of anything or will they pick everything that falls in their path up?