Kei Enjoji is the main character of _Kizuna_. He isn't the legal son of a yakuza's group chief, so he has to leave the main house. After he left, he finds Ranmaru and falls in love with him. Even if he is not the legal son of the chief of the yakuzas, a rival gang tries to kill him, but they fail and they almost kill Ranmaru. Ranmaru doesn't believe he could walk again, and Kei tells him that he will be his left arm and his left leg. So he wants Ranmaru to get better because he loves him too much. Ranmaru makes efforts over efforts, and eventually walks again. So begins their love! After this, Kei found his little brother, Kai, who is the legal son. Kai and Kei don't get along well because Kai likes Ranmaru, but Kai lets it go when he sees how much Kei and Ranmaru love each other.