A boy is seen struggling and dying of hunger while thinking of the food he used to eat at the orphanage. The boy's name reveals to be Atsushi. He was driven out of their orphanage without anything to eat, and a place to sleep. While pondering on the thought of stealing to survive, he notices a man drowning in the river and immediately rescues him.
Dazai introducing himself.
The man asks Atsushi if he is the one who saved him and tells Atsushi that he hindered his attempt at suicide. The man then apologizes to Atsushi for causing him trouble because he thought it would be a clean suicide. Atsushi's stomach began to growl. Hearing this, the man asks Atsushi if he was hungry, Atsushi reveals that he has not eaten for three days, the man replies that he is also hungry but his wallet got washed away in the river.
Another man appears on the other side of the river named Kunikida who is the man's associate. The man then offers to let his associate treat Atsushi. The man then asks his name and Atsushi replies with "Atsushi Nakajima". Kunikida shouts at his associate who reveals to be Osamu Dazai, to not use his money without his permission.
Atsushi with Kunikida and Dazai.
The three go to a soba restaurant. Kunikida reveals that they are in the middle of a work request to exterminate a beast. Dazai reveals that recently a man hunting tiger has been causing a lot of trouble in Yokohama. After hearing Dazai, Atsushi becomes shocked and insists that he'd better go. Kunikida stops him and Atsushi firmly says that a human cannot defeat it. Kunikida then asks Atsushi if he knows something about the man-eating tiger. Atsushi still tries to escape while saying that the tiger is after him. Kunikida restrains him and tells Atsushi that the agency specializes in violent cases. Kunikida then orders Atushi to tell them everything he knows but Dazai interrupts him saying that information should be gathered through questioning as the director always say.
Dazai asking Atsushi for help to catch the tiger.
Atsushi then begins to confess that the orphanage he lived in was destroyed by the tiger, the field was completely ravaged, there were no casualties but the orphanage was on the brink of losing. Atsushi tells them that he was kicked out to reduce the people they feed. Kunikida then asks Atsushi what he meant that the tiger is there to kill him. Atsushi responds that after he left the orphanage, the tiger chased him in the city. Atsushi further tells them that he cannot remember how he escaped as he was dizzy and hungry. Dazai asks him when did it happen and Atsushi replies that he left the orphanage two weeks ago and saw it at the river four days ago. Kunikida then tells them that the tiger's victims were also seen in the vicinity and the tiger was also seen in the Tsurumi River four days ago. After some thinking, Dazai asks Atsushi is he is free and helps them in their tiger hunt and there will be a reward of him. Dazai gives a note to Kunikida to give to the president.
Dazai and Atsushi waiting for the tiger's appearance.
Later that night, Dazai and Atsushi are waiting at the warehouse. Atsushi asks Dazai if the tiger will really come at the warehouse and Dazai says that it will come and tells him not to worry since the tiger is no match for him. Atsushi then tells Dazai that he admires his confidence, unlike him who was always called "good for nothing", and that trash like him should just probably die somewhere.
Dazai then looks up at the sky and tells Atsushi that any moment now, the tiger will come. A sound was heard from the warehouse which made Atsushi startled. Atsushi continues to panic saying that the tiger will eat him. Dazai then tells Atsushi how it is strange that the orphanage kicked him considering it was an orphanage and considering that the orphanage is in a brink of closing, kicking one or two children would not help that much. Dazai then continues to tell Atsushi that he came to the town two weeks ago, the same as the tiger.
Dazai nullifies Atsushi's ability.
While Dazai continues to talk, Atsushi transforms into the tiger. Atsushi, in the form of the tiger, starts to attack Dazai however he successfully avoids them. Dazai then touches the tiger and nullifies it turning it back to Atsushi. Atsushi loses consciousness and falls to the floor. After nullifying the ability, Kunikida arrives at the warehouse and learns that Atsushi is the tiger. Dazai reveals that he has the power of the tiger and doesn't seem to retain his memories after hi transform.
Kunikida then reveals the note Dazai gave him which states "The tiger will appear in the Western Warehouse in District 15. Build a perimeter to ensure it cannot escape" and tells Dazai that he even deployed those that are off-duty, revealing other agency members: Akiko Yosano, Ranpo Edogawa and Kenji Miyazawa. Dazai then tells them his plan for Atsushi and for him to join the agency.
Atsushi wakes up at a dorm.
Dazai suggests allowing Atsushi to join the Agency to the other members, immediately Kunikida explodes with a "WHAAAAAAT?!". The scene cuts to Atsushi waking up on a floor bed in an unfamiliar room, confused about where he is and why the wake-up bell of the orphanage hasn't gone off, or why morning roll call hasn't taken place.
Suddenly, a flip phone beside the bed begins to ring and Atsushi flinches, struggling to work the phone until he picks up. Dazai asks Atsushi how his new dorm is and if he slept well, Atsushi remembers the events that happened yesterday and thanks Dazai for the spacious place to live. Dazai is glad and asks Atsushi a favor, "Help, I'm dying.".
Dazai tries a suicide method.
Atsushi finds Dazai wedged in an old oil bucket, Atsushi shows visible confusion. Dazai causally asks Atsushi to save him quickly, and Atsushi asks him what's going on, Dazai asks what he think is going on. Atsushi says he thinks he is hallucinating. Dazai explains that he's trying a method of suicide, but says it's not fatal, just extremely painful.
Atsushi doesn't see why Dazai is complaining and Dazai cringes, saying he doesn't want suicide to hurt so much. Atsushi pretends to understand Dazai's reasoning and lays the oil drum to its side, helping Dazai out of it. As Dazai and Atsushi begin to walk, Atsushi asks if Dazai asks his colleagues for help. Dazai says he did, telling them "I'm dying", to which they replied "Hurry up and die" or "Good for you" before hanging up. Atsushi asks Dazai where they are going and Dazai says he's assigning something to him, explaining that the agency has new leads for their case and they need to drop by there.