Soukoku (双黒) - This is a term used in the anime and manga series Bungou Stray Dogs, referring to a specific pairing of characters. It translates roughly to "Double Black" or "Twin Black."

Chuya
Nicknames:
"Double Black" (paired with Osamu Dazai);
"King of the Sheep" (formerly);
"Arahabaki";
Mr. Fancy Hat (by Ranpo Edogawa);
"Slug" and "Hat Rack" (by Osamu Dazai) and others.
Appearance
Height: 160 cm.
Weight: 60 kg.
Hair color: orange-red.
Eye color: in the anime - gray-blue.
Blood type: B (III).
Appearance: Short but muscular. Side-swept bangs cover the right side of his face; his hair is pulled back into a ponytail and combed to the left. He often wears a hat.
Clothing style: white shirt, dark blue trousers, black choker, bolo tie, brown shoes, black gloves.
Personality
Temperament: hot-tempered, arrogant, sometimes rude.
In battle: enjoys battles, is proud of his reputation as the strongest fighter in the Port Mafia, and mocks his opponents.
Judgment: Able to remain cool and analyze the situation in the heat of battle.
Loyalty: Fanatically devoted to the Port Mafia; finds betrayal unbearable, respects his subordinates and demands their loyalty.
Contradictions: despite his cruelty, he is reasonable if not provoked; he can be naive (as in the episodes with Dazai's dilemmas).
Priorities: The well-being of the Port Mafia is the top priority; willing to go to extreme lengths to protect the organization.
Biography and connections
Position: One of the five leaders (members of the Executive Committee) of the Port Mafia.
Past: Former partner of Osamu Dazai; formerly the "Sheep King".
Internal conflicts: In the past, he searched for his place in the world, questioned his own humanity due to his connection with Arahabaki
Capabilities
Main Ability: "Vague Sadness" - Allows one to manipulate gravity and the force of gravity of objects in physical contact with Chuuya.
Additional form of power: "Corruption" (related to Arahabaki's influence).
Preferences and habits
Likes: hats, fighting, drinking, music.
Dislikes: Osamu Dazai (complicated relationship with former partner)
Birthday: April 29

Dazai
Appearance
Osamu Dazai is a young man with the following traits:
short, partially wavy
dark brown hair (bangs frame the face, individual strands are gathered in the middle);
narrow dark brown eyes;
tall and slender silhouette;
bandages all over the body
Physical parameters:
height: 181 cm;
weight: 67 kg;
blood type: AB (IV);
Birthday: June 19.
Personality
Dazai is a mysterious and contradictory figure. Key character traits: cockiness and a penchant for jokes (he often teases his colleagues, especially Kunikida Doppo);
cheerfulness and drama in behavior; self-sufficiency and composure in critical situations;
sharp mind and insight (quickly notices details, for example, immediately understands the nature of Atsushi's abilities);
strategic thinking and the ability to develop long-term plans; a tendency to manipulate and use “dirty” methods to achieve a goal;
caring for his comrades (especially those in whom he sees potential, such as Atsushi).
Past and connections
former member of the Port Mafia Executive Committee, Ogai Mori's right-hand man; partner of Chuya Nakahara during his time in the mafia (their duo was nicknamed "Double Black");
a master interrogator and tactician who has earned the trust of Ogai Mori;
Sakunosuke Oda's friend who convinced him to "choose the good side" before his death;
Ryunosuke Akutagawa's mentor (who trained him harshly in the past).
Ability
"Confessions of a Defective Person" (L5 #, Ningen Shikkaku):
allows to neutralize
another esper's supernatural abilities through direct physical contact; does not work over distance; always active on contact.
Habits and preferences
drinks black tea (often seen with it in cafes); drives poorly;
loves crabs, MSG and alcohol;
doesn't like dogs;
Ideal partner type (according to him): a person who is ready to commit double suicide with him