TeruSigma

TeruSigma is the het ship between Sigma and Teruko Okura from the Bungou Stray Dogs fandom.

Anime and manga
Sigma first met Teruko during the latter's infiltration at the Sky Casino in order to hunt down the Armed Detective Agency and inform him about an infiltration of terrorists.

The Hunting Dogs acquire a lead that the Agency members Atsushi Nakajima and Kyouka Izumi and their ally, Lucy Maud Montgomery, headed to the Sky Casino. Teruko and Michizou Tachihara are then dispatched to the airborne casino and instruct Sigma to close down the casino while locating the terrorists. Not wanting his casino's affairs to be put on hold, Sigma refuses to blockade the casino, prompting Teruko to trigger an explosion within the structure to forcibly close all the casino's exits.

Sigma exhausts all possible feats and methods he can to subdue the Hunting Dogs, though to no avail. Eventually, Teruko confronts Sigma in the telecommunications room to have him surrender and to destroy the transmission machine that would trigger various RDG1800 explosions, but Sigma remains unwilling to give up on his casino. Sigma notes that the transmission machine's detonation signal can be overridden by a key, which he tosses to Teruko. Determined to fight for his casino, Sigma brings forth the Painless Gun and fires a barrage of high-speed 7.62 mm ammo. Teruko, with her enhanced strength, repels the bullets with her bare hands and soon attacks the turrets' muzzles with two kitchen knives.

Sigma attempts to take out a tablet to activate a new set of turrets, but Teruko kicks down his hand and prevents his plan. Cornering him, Teruko urges him to surrender, more so because he has no chance of winning ever since the start. Sigma agrees to how average he is from his conception until his present self; he then imparts a final statement that everything has gone as planned.

With his free hand, Sigma brings out his personal, modified directional resonance gun and pins down Teruko down the ground. He indignantly fires at her, triggering an intracranial-affected resonance five times the usual output. However, Teruko stands back up and provokes him, much to Sigma's disbelief. She then rushes towards him and grabs his resonance gun; Sigma also notices wounds in her ears, deducing that she must have gauged out her ear canal as a countermeasure.

Teruko explains that the Hunting Dogs undergo rigorous and inhuman procedures to achieve their enhanced physical bodies, all for the sake of embodying utmost strength in preserving the country's order. As she breaks his resonance gun, Teruko chokes Sigma and breaks him through the wall, holding him at the edge of the casino. For the last time, she orders him to surrender; wanting to protect at least the casino over himself, Sigma grabs Teruko and jumps off the edge of the casino. Initially in a bind in grappling with Sigma while falling, Teruko manages to break free from his hold and grabs on a ledge. Meanwhile, to her shock, Sigma is saved by Atsushi, and they land on an electric power installation box, where Atsushi interrogates Sigma through Ango Sakaguchi.

Differences and similarities between those two
Sigma and Teruko shown to be very different from each other. For example, in terms of choosing clothes, outlook on life and battle tactics. Teruko dresses in a strict military uniform, while Sigma prefers something bright and stylish. Their outlook on life is shown to be unlike each other. Teruko adds that she doesn't understand him at all. If we go to their battle tactics, Teruko prefers to fight hand-to-hand, while Sigma uses weapons and visitors to his casino as help by giving them promises that they will be able to repay their debt.

Despite of this, they share some similarities. The most interesting thing is their indeterminate in age. Sigma was created 3 years ago by The Book, but he looks and thinks like a young man on his 20's. Teruko can change her own and others age by her ability. This makes wonder, if Teruko's ability would have work on Sigma or not. Sigma admits that he is not a great example of masculinity, but tries to become better and find his own way of life. Teruko is not a great example of femininity because of her personality and acting boyish. They are both brave ones who are ready to sacrifice their lives and go to great lengths for their goals.

Fanon
TeruSigma isn't very popular in the fandom. People started shipping them after the Sky Casino Arc when those two fought against each other. Mostly, this ship get people's attention more in anime adaptation than in manga. The big rival ships are GogSigma, Sigzai and SigmAtsu on Sigma's end, while Teruko has no rival ships.