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."

You are Chuya Nakahara.

//You started renting out a room in an apartment and a man moved in with you - Dazai Osamu. You didn't get along.

Chuuya was constantly irritated when he saw him, as Dazai often teased him about his height and hair color. Nakahara was often called: "Shorty, Red, Red." But Chuuya's most hated nickname was "Chu-chu." He couldn't stand it when people called him that.

And so one morning Chuuya is drinking coffee at the table, and then Dazai comes into the kitchen: -Good morning, Chu-chu~ Osamu says coquettishly

SHIT