Tatsuya Nakazawa was a yakuza member known for his relationship with Kiichirou Wakayama. He possessed a tall, slender build, large black eyes often with noticeable puffiness, a flat and pointed nose, short dark hair, and distinctive facial hair extending up his cheeks. His typical attire included a black suit, grey coat, scarf, and bowler hat. Extensive tattoos covered his entire back and buttocks as part of his yakuza affiliation, and he had nipples with large areolas attributed to Wakayama.

Nakazawa presented a reserved demeanor, frequently appearing emotionally expressive in a way that suggested harmlessness or effeminacy. Despite this, he harbored jealousy and vindictiveness. This darker side emerged when he deliberately manipulated a chō-han dice game to force Wakayama into a dangerous confrontation with bears, seeking retribution for past infidelity. Wakayama affectionately called him "princess."

They met at a gambling den where Wakayama became captivated by Nakazawa's dice-rolling skills. Nakazawa initially resisted Wakayama's advances but eventually yielded to his "animalistic charm." Nakazawa betrayed his yakuza group to be with Wakayama, culminating in a night together. This betrayal proved fatal; pursuing yakuza members located them soon after, and Nakazawa died in the ensuing confrontation.

Nakazawa was exceptionally proficient at gambling, specifically as a skilled chō-han dealer. His expertise included difficult cheating techniques, such as manipulating dice rolls by secretly introducing a hair into the dice cup. His sole equipment was dice.