Cho Hakkai is a tall, lanky young man with messy brown hair and green eyes, his right eye replaced by a magitech prosthetic offering minimal vision, requiring corrective glasses. He favors slightly baggy clothing reminiscent of an absent-minded scholar, including a white shoulder cloth to shield against scratches from his pet dragon Hakuryuu. Three silver cuffs on his left ear serve as magitech limiters, suppressing demihuman traits to maintain his human appearance. Removing these reveals his youkai form: pointed ears, clawed fingernails, a slitted yellow left eye, and skin etched with swirling black vine-like markings.

Born human as Cho Gonou, he was orphaned and raised by Catholic nuns, struggling socially and rejecting religious doctrine. He later taught school and fell in love with Kanan, unaware she was his twin sister until their adult reunion. They lived together as lovers despite societal taboos. When the youkai lord Hyakugan Maoh abducted Kanan, Gonou slaughtered half the complicit village before storming the castle to kill Maoh and nearly all his followers. Discovering Kanan pregnant with Maoh's child, she revealed their incestuous bond and committed suicide with Gonou's knife. The sole survivor, Chin Yisou (Maoh's son), mortally wounded Gonou and dripped his blood onto him, fulfilling the legend that bathing in a thousand youkai's blood triggers transformation. This turned Gonou into a hybrid youkai.

Declared dead, he was renamed Cho Hakkai by the divine Three Aspects as penance. His name alludes to Buddhism's Noble Eightfold Path, implying restrictions like abstaining from intoxication—reflected in his inability to get drunk despite enjoying sake. He initially harbored intense self-loathing for his youkai nature and violent past, though cohabiting with half-youkai Sha Gojyo tempered this. Within the Sanzo party, he assumes caretaker duties: cooking, cleaning, mediating conflicts, and driving their vehicle (Hakuryuu as a jeep). His demeanor blends gentle patience with dry wit, masking deep guilt, melancholy, and suppressed rage. This volatility erupts when allies are threatened, provoking ruthless retaliation.

His primary ability is kikou jutsu (chi manipulation), deployed for healing, defensive barriers, and energy blasts. He demonstrates proficient martial arts and surprising strength, having once eradicated youkai hordes with only a dagger. Removing his limiters unlocks full youkai powers: heightened strength, speed, agility, and the capacity to manifest his vine markings as tangible bindings that conduct energy. This transformation risks失控 under influences like the "minus wave," amplifying aggression to lethal extremes. Key relationships define him: with Gojyo, he shares a marriage-like bond of mutual reliance; with Son Goku, he exhibits protective mentorship anchored by Goku's role in preserving his humanity; and with Genjo Sanzo, he maintains unwavering respect for their nominal leader.