He and she are the world's top gold medal mercenaries, and they can be called the "double peer" in the world. But they are human beings with flesh and blood and their own feelings, not machines that can be controlled by others.
He had known her for 18 years and been in love for five years, but their relationship was extremely opposed by the organization. He is a genius, but she is not. The organization wants his machine-like and precise mind. They valued him, used him, and tried to control him.
The organization took advantage of his feelings for her and said they could let her go as long as he stayed. He agreed, but he didn't know that they deceived him and wanted to use his hands to kill her, remove her as a stumbling block, and let him cut off the love between him and her with his own hands.