Episode 4

The Tragedy of the Fatalist (運命論者の悲み,) is the 4th episode of Bungo Stray Dogs anime series. It aired on April 28, 2016.

Synopsis
Though saved from the Port Mafia by Dazai's intervention, Atsushi feels responsible for bringing trouble to the Agency's door. Rather than risk another attack because of him, Atsushi decides to leave the Agency and makes a call to the Port Mafia...

Summary
As Atsushi awakens after his encounter with Akutagawa, Kunikida advises him not to panic despite having a bounty on his head. Atsushi notices Kunikida's dire attempt to hide his nervousness, suspecting that the Agency must be in grave danger because of his doing. Kunikida warns him that the mafia shall soon return for him and therefore advises him to think about what he can do.

During a mafia operation, Ryūrō Hirotsu of the Port Mafia's Black Lizard heads an infiltration in a workers' base suspected of selling Port Mafia cargo to the black market. After finding evidence that confirms their suspicion, Hirotsu orders his cohorts to kill the workers; the base is later bombed after the massacre. As the police arrive, Atsushi heads to the scene and hears about the danger of the Black Lizard from the crowd.

Thinking that they might soon attack the Agency in a worst-case scenario, Atsushi decides to quit the Agency. He contacts Higuchi and challenges her to catch him, thinking that doing so would keep his comrades away from harm. As Atsushi bids his farewell to a confused Kunikida, Higuchi assembles Black Lizard to raid the Agency. Meanwhile, Akutagawa visits an imprisoned girl and attacks her with Rashōmon. In the end, he lets her live after seeing her unflinching resolve even in the midst of his attack.

Black Lizard arrives at the Agency's front door and barges in. As they begin their assault, the wandering Atsushi hears gunshots coming from the Agency's direction. He rushes back to their headquarters only to find Kunikida, Kenji, and Yosano easily overpower the enemy's forces. As Atsushi realizes that the Agency seems to be more violent than Port Mafia, Kunikida reprimands him for leaving his post despite now being a member of the Agency. Upon hearing these words, Atsushi chuckles and weeps seemingly out of joy, albeit trying hard to hide his tears from Kunikida and the others.

Manga and Anime Differences

 * In the manga, Atsushi carries a huge load with him when he leaves the Agency. In this episode, he merely brings with him his satchel.
 * The manga chapter concludes with Ranpo announcing his leave for a murder case and Kunikida assigning Atsushi to accompany the detective, which is not depicted in this episode.