Souichirou Arima, born to Reiji Arima and Ryoko, endured severe abuse from his mother after she learned Reiji would receive no inheritance. Ryoko beat him bloodied, stabbed him with scissors, and starved him near death, while also isolating him socially. Rescued by his father at age three, he was placed with his uncle Shouji and aunt Shizune Arima. However, rejection from most Arima relatives followed due to his parents' status as family disgraces. At Hokuei High School, Souichirou meticulously crafted an image of perfection: excelling academically, achieving national kendo championship status, and maintaining a handsome, composed facade. This stemmed from deep fears of inheriting his parents' destructive traits and a belief that flawlessness prevented rejection. Initially fixated on fellow high-achiever Yukino Miyazawa, unaware of her resentment, he blackmailed her into doing his schoolwork after discovering her hidden, imperfect self. Their relationship evolved from rivalry to mutual understanding when Yukino learned his perfection masked childhood trauma. They became each other's first genuine friends and then romantic partners. As their relationship deepened, Souichirou's unresolved trauma manifested as intense jealousy and possessiveness towards Yukino, permitting friendship only with those like Hideaki Asaba, whom he deemed non-threatening. His "dark side" surfaced through violent impulses, including a sudden sexual encounter in the school library which he later interpreted as non-consensual due to Yukino's initial hesitation. Overwhelming guilt drove him to self-harm with a box cutter. Yukino intervened, injuring herself to demonstrate solidarity and acceptance of his entirety. This pivotal incident forced him to confront his past. Reconnecting with his father, jazz pianist Reiji, during a visit to Japan aided Souichirou's healing, strengthening their bond over ten days. Yukino's unwavering support and insistence on shared suffering taught him trust. He gradually opened up to friends and adoptive parents, abandoning his facades and accepting his multifaceted identity, recognizing his capacity for cruelty while choosing not to be controlled by trauma. After high school, Souichirou married Yukino following her pregnancy. They had three children: daughter Sakura and twin sons Suoh and Ai. Defying family expectations of a medical career, he pursued law enforcement, becoming a police officer. By age 30, he achieved the rank of highly decorated inspector and prepared for commissioner exams. His marriage to Yukino solidified his journey toward emotional stability, acknowledging the past as part of him without dictating his actions. Later, his daughter Sakura formed a significant bond with Hideaki Asaba, who helped raise her during Souichirou's police training. Sakura declared love for the significantly older Hideaki, who eventually accepted her feelings as destined, integrating him into the Arima family structure.