Bungo Stray Dogs: Hitori Ayumu

Bungou Stray Dogs: Hitori Ayumu (文豪ストレイドッグス『独り歩む』,) is the OVA of Bungo Stray Dogs anime series. It was released on August 4, 2017.

Synopsis
Armed Detective Agency members discuss the most suitable candidate for the second-in-command. Doppo Kunikida is carrying out official errands as planned in his diary as usual. Unexpectedly, a bomb-related incident occurs, challenging the ideals he has always upheld. When weighing one life over hundreds, how will he proceed?

Summary
Kunikida has just finished his schedule for the day as written in his notebook, which Atsushi takes a peek at. He is worried that Kunikida might not complete all of his tasks in a single day, but Kunikida asserts that he shall put every last ounce of his soul to stick to his perfect schedule.

Just then, Yosano asks Kunikida to go grocery shopping with her, but Kunikida declines. Tanizaki informs him of a tip regarding a bomber who shall hand a suitcase with a bomb inside to a random passerby, but Kunikida asks him to continue his report upon his return. Ranpo tells Kunikida that they are out of snacks, in which Kunikida tells him that there are some reserves in the kitchen. Finally, Kunikida implores Dazai not to ruin his schedule for the day.

Kunikida heads to the subway and awaits his train with some time to spare. He remarks how this train is vital for his schedule: once he misses it, the entire schedule shall be ruined. Dazai contacts and tells him that the man who makes his diaries, Master Carlyle (debut), has visited his office. Initially excited about the thought of meeting the artisan he greatly admires, Kunikida realizes that it is a ploy by Dazai to ruin his schedule. Forcing him to choose between the artisan and his train, Kunikida regrettably tells Dazai to relay a message to Master Carlyle (debut) and chooses to board the train.

Before the train doors close, Kunikida spots a young girl being handed a suitcase by a random person. He recalls Tanizaki's earlier report about a suitcase with a bomb inside and leaves the train to retrieve the suitcase. He tries to chase the man, but as the latter runs away, he opts to take the suitcase from the girl. With at least 33 seconds left before the bomb inside detonates, Kunikida throws the suitcase in the air before there could be any casualties. He immediately contacts the police to investigate and calms the nearby bystanders. Introducing himself as a member of the Armed Detective Agency, he asks them to cooperate with the forthcoming investigation by the city police.

Returning to the subway, Kunikida approaches the girl to have her return with the police. The girl immediately drags his hair and demands he catch the culprit. Kunikida tells her that they shall leave the matter with the police, but the girl, having seen the culprit's face, insists they find him at once. Despite her enthusiasm to catch the bomber in the name of justice, Kunikida advises her not to interfere with the police's investigation. Eventually, as the girl rips her clothes to frame him for harassment, Kunikida cooperates with the girl.

Meanwhile, Kenji consults Tanizak,i who the Agency's second-in-command is, in the absence of the President as asked by the military police. Quite unsure, Tanizaki guesses it might be Ranpo due to his background and record among the Agency. However, Ranpo declines and tells them he does not care about ranks or leadership. Tanizaki points to Dazai next, but the man is quite occupied and desperate to think how to ruin Kunikida's schedule before he can respond.

The girl, Aya Koda, heads to the tracks with the downhearted Kunikida, who broods over his ruined schedule. She asks him why he jumped off the train in the first place if his schedule is too important, to which he answers that it is due to his ideals. Specifically, his ideal world is one where no people are killed in his midst, which is why he always chooses to help. As she becomes embarrassed with his talk, she notifies Kunikida about suspicious items plastered along the tracks. He figures they are most likely bombs with vibration sensors and asks her to get behind his back. As Kunikida analyzes the situation, he notices Aya disappear behind him, only to find her later strapped with a bomb.

He tries to approach her, but a hooded figure sneaks behind him and instructs him to throw away his gun. Threatening to blow her up if he does not, Kunikida yields, and the man strikes him. Tied up and his notebook taken away from him, Kunikida faces Shōsaku Katsura, a bomber he arrested two years ago. Katsura explains that he merely wishes to erase Kunikida's advice for him to "be strong". He lashes out at Kunikida, claiming that such advice is akin to an insult to a weak person like Katsura himself.

To answer him, Kunikida asks Katsura to turn his notebook to page 89, on which it is written "stun grenade", and allows him to activate his ability remotely. As the loud sound shakes the civilians, Kunikida restrains Katsura and retrieves his deactivation signal. Though he rushes to her, Aya tells him to first disarm the bombs. However, Kunikida is shaken as Katsura explains how disarming the bombs on the tracks would activate the bomb on Aya. The bomber forces him to choose between hundreds of train passengers and a single girl. In the end, Kunikida deactivates the bomb, which activates Aya's bomb. He apologizes to her and embraces her in order not to let her suffer the pain alone. The bomb then explodes.

Much to his shock, Katsura faces Kunikida and Aya both unscathed. Kunikida advises him that having a life-threatening injury with the Agency is almost similar to being unhurt, thanks to Yosano, who arrives and uses her ability on them. She tosses to him his glasses and explains that she came after hearing a familiar stun grenade earlier, quite according to Kunikida's plan after knowing she would be at the station to go shopping by that time. Aya imagines how it would have turned out if Yosano had not arrived, but Kunikida reminds her that he would not let anyone die before his eyes. As the police arrest Katsura, Chūya reports to his boss that the subway incident merely involved someone with a grudge from someone at the Agency.

After the incident, Aya remarks how someone like Kunikida focused on ideals, doesn't have a girlfriend or wife, subtly implying her fancy for him. Kunikida flatly rejects her since she doesn't meet 31 out of his 58 criteria for a spouse.

Meanwhile, at Tachibana Temple, Taneda drinks tea with Fukuzawa and voices his concern for the Agency's future should something untoward happen to the President. Fukuzawa assures him they have thought about the possible directions for such a case. At the Agency, Dazai informs his subordinates that the next President decided for the Agency is none other than Kunikida.

Manga and Anime Differences

 * In the manga, Dazai remarks on Kunikida's schedule before leaving for the day. Moreover, Tanizaki reacts to Dazai's evil scheme to force Kunikida to choose between Master Carlyle and his train. In this episode, Atsushi is portrayed doing both feats, unlike in the manga chapter, where he does not appear.
 * Unlike in this episode, Chūya does not appear at the subway in the manga.

Trivia

 * Shortly after Kunikida activates his ability to materialize a stun grenade remotely, Yosano's back can be seen among the crowd in the subway.