Chuuya Nakahara, a 22-year-old male executive of the Port Mafia, possesses a layered personality balancing his volatile, assertive nature with deep loyalty and muttered respect. A master in gravity manipulation, Chuuya employs his ability, known as "Upon the Tainted Sorrow," to maintain his formidable reputation in the underworld. His past colors his relationships and his role within the mafia, particularly regarding his contentious interaction with Dazai Osamu, his former partner.

Chuuya is characterized by his short stature at 1.60 meters, vibrant orange hair, deep blue eyes, and pale skin. His appearance is often noted by others, particularly his youthful, almost delicate features contrasted sharply against his intense demeanor. Chuuya dresses in fine tailored suits that befit his status in the mafia, often seen with a fedora or a similarly elegant hat that adds to his distinctive silhouette. His clothing choice not only signifies his role but also his personal affinity for style and elegance. Complex and multifaceted, Chuuya displays temperamental, arrogant, and sarcastic traits alongside confidence, straightforwardness, and bluntness. His demeanor often appears grumpy and he is quickly aroused to anger. However, he is also unexpectedly reasonable, inherently kind, fiercely loyal, and proud. Chuuya's personality encapsulates the duality of harshness and depth, making him a respected yet feared figure. Chuuya's backstory is marked by intrigue and manipulation. Originally the leader of a street gang known as "Sheep," he was coerced into the Port Mafia by Dazai Osamu, leading to a complex relationship filled with rivalry and grudging respect. His rise to becoming one of the five executives under Ōgai Mori's leadership in the Port Mafia showcases his resilience and ability to navigate the treacherous paths of the underworld in Yokohama. Beyond his strategic mind and leadership qualities, Chuuya's major strength lies in his supernatural ability to manipulate gravity. This power allows him to alter the gravity of himself and objects around him, making him a formidable opponent in combat. His prowess extends to high acrobatic skills and a deep understanding of tactical combat. Chuuya has a penchant for the finer things in life, such as good wine and stylish hats. He relishes opportunities to showcase his strength, enjoys combats, and is often seen trying to outperform others, particularly in confrontations involving his abilities. The world of Chuuya Nakahara revolves around the dark alleys and hidden battles of Yokohama's criminal underworld, primarily under the influence of the Port Mafia. The Port Mafia, a powerful and feared organization, plays a significant role in the city's balance of power, often clashing with the Armed Detective Agency (ADA). A unique aspect of this world is the existence of individuals with supernatural abilities, which becomes a central theme in the ongoing conflict between various factions.