Episode 1

Fortune is Unpredictable and Mutable (人生万事塞翁が虎,) is the 1st episode of Bungo Stray Dogs anime series. It aired on April 07, 2016.

Synopsis
Driven out from his orphanage, Atsushi Nakajima wanders the streets of Yokohama on the brink of starvation. Determined to live, a chance encounter with a drowning stranger changes his fate...

Summary
Atsushi Nakajima is on the brink of death, laying by the banks of a river under a bridge. Determined to keep living despite the hateful comments of his past orphanage to him, he resolves to rob the next man he sees. Almost immediately, he sees a man floating down the river and ends up saving Osamu Dazai from a comical attempt on his own life. Noticing the hunger of the boy, he invites him to eat at the expense of his partner, Doppo Kunikida.

While chatting, they come across the topic of their careers. The pair acknowledge that they are from the Armed Detective Agency, a renowned group of private eyes armed with supernatural powers for cases too dangerous for the likes of the police. Kunikida questions Atsushi if he had seen a white tiger roaming around the town recently, inducing a response of fear on the part of the boy. Atsushi panics, claiming that the white tiger had been following him from the past two weeks and was out for his blood. In the end, Dazai takes him to a warehouse to apparently lure out the beast.

While waiting, Dazai remains calm throughout the hour, whilst Atsushi is convinced that the tiger had arrived and was stalking the shelves of the building. Keeping a cool face, Dazai states that Atsushi had seen the tiger for two weeks and had seen the beast for the same amount of time that multiple accounts had traced back to. He had also been in the same towns as the tiger, revealing that Atsushi himself had a skill and could transform into the creature under the light of the full moon, not unlike a werewolf. When he transforms and attempts to attack him unconsciously, Dazai activates his own ability and stops him. When Atsushi wakes up, he finds himself surrounded by most of the Agency, where Dazai reveals him as the tiger and recruits him to the Agency, much to his confusion.

Manga and Anime Differences

 * In the manga, after he decided to rob the first person he sees, Atsushi immediately sees Dazai drowning in the river. In this episode, he first encounters a speeding motorcycle rider and a platoon of training military police before seeing Dazai and saving him from drowning.
 * Kunikida carries a gun with him in the manga, though he does not appear to have one with him in this episode.
 * In this episode, after Dazai nullified his ability, Atsushi sees his right hand still partially transformed into a tiger's paw. This does not happen in the manga, as Atsushi remains unconscious throughout the rest of the night.

Trivia

 * The title of the episode derives from a Japanese proverb (人間万事塞翁が馬, ningen banji saiō ga uma).
 * The episode's title card contains text from Rashōmon by, The Moon Over the Mountain by and No Longer Human by.
 * The episode depicts how Atsushi first meets Dazai drowning in the river as a suicide attempt. The real-life died in a similar fashion, albeit.