Episode 46

A Dream of Butterflies (をむ,) is the 46th episode of Bungo Stray Dogs anime series and the ninth episode of the fourth season. It aired on March 1, 2023.

Synopsis
Port Mafia boss Mori wants Yosano to join them in exchange for assisting the Detective Agency through their crisis. Yosano reveals why she would rather not.

Summary
Yosano decides to push through with the transaction with Francis despite Mori's caution that it might be a trap. As they face Yosano, Tanizaki and Kenji ask about her aversion to joining the Port Mafia, urging Tanizaki to volunteer instead and ask her what happened with her and Mori. Yosano then reveals that Fukuzawa and Mori called off their alliance in the past and are now enemies because of her.

Fourteen years ago, an 11-year-old Yosano was recruited as a student medic by then medic adjutant Mori to Tokoyami Island, a major battlefield towards the war's conclusion. With Yosano's ability, soldiers were healed rapidly and with ease. Yosano also met a gifted private who gave her a butterfly hairpin from his own ability, thanking and calling her an "angel".

The soldier noted that his ability was far from changing the world unlike hers, displaying his knowledge on the Skill Doctrine that allowed abilities to be used in the war for advantage. To prove this, he then revealed Mori to have brought Yosano into the unit as part of his classified "Immortal Regiment" paper. Oblivious to the scheme, Yosano stated that she only wanted to save others' lives, only for Mori to cut off and direct her to the other patients.

Later, the soldier's outgunned and outnumbered unit was almost decimated in an explosion; Yosano eventually healed them from their physical injuries, exhibiting exhaustion during her assignment. She expressed frustration at how she could heal physical wounds but not their minds from the toll of war, claiming that she was only healing the soldiers for them to die again.

The soldier assured her that, keeping count of the times she saved him and reaching the count to be five—the same character for the word "correct"—on his dog tag, something correct would then get created in the world. Moreover, he told her that she was the reason why he still had the chance to meet his family after saving him all the time, expressing his gratitude for her presence with them.

However, the war worsened, and the situation entailed the soldiers to continue fighting instead of retreating because of Yosano's ability. Witnessing continuous horrors, Yosano was once ordered by Mori to heal the soldier to have him return to the battlefield at once, but Yosano refused. He told her of how fighters and weapons gradually lost to more advanced ones in past wars, with abilities now being the ones changing war. Her role, therefore, was to make the military understand such change if she did not want the nation to fall. She continued to decline his order; hence, Mori shot the soldier, forcing Yosano with no other choice to heal him.

With no one allowed to leave the battlefield, Yosano lists down the soldiers who died who could have left with mere injuries if not for her ability. Because she was there, there was no retreat and no chance to "lose", believing that she had taken away such human right. Eventually, one of the troops attempted to kill Yosano to stop their suffering, but to no avail.

Later, while looking for her missing butterfly pin, Yosano is contacted by the soldier, confessing that her ability and its correctness taught him that everyone has limits. Remembering how he previously called her an angel, he retracted it and called her an angel of death. He then bid her to tell his family goodbye before cutting contact. She soon found him having committed suicide, his tallied dog tag, and a note stating that she was "too correct", leaving Yosano gravely aghast.

Yosano soon continues telling Tanizaki and Kenji more about what happened afterwards. Back then, she was arrested for trying to blow up the carrier and was subsequently placed in an isolation facility. Tanizaki wonders if the Agency was the one who rescued her, only for Yosano to quip that it was actually the worst possible person: Mori found her three years after the war in an attempt to use her ability to fight the erstwhile Port Mafia boss.

Before Mori could do so, Fukuzawa intercepted and fought the doctor over Yosano's welfare. While Fukuzawa condemned his heartless, hellish plot for the girl, Mori argued that she would be the pillar of the Tripartite Framework and therefore the city's peace. With their clashing ideologies, Fukuzawa and Mori mutually ended their alliance with each other.

Meanwhile, Ranpo moved Yosano away from the battle, though Yosano asked him to take her back, considering her ability to cheapen human lives and therefore made her unfit to live. Ranpo asked her to merely stop using her ability because his own ability was the only one needed after all. As he claimed he could solve any problem, he handed back her missing butterfly pin that he found in the carrier.

She soon turned to Ranpo on what she should do from then on; Ranpo answered that she should live with and join the Armed Detective Agency not for her ability but for her kindness, leading Yosano to weep out of intense emotions.

At the Mafia base, Yosano, Tanizaki, and Kenji head out to go to the transaction site. Yosano ushers her fellow detectives out the door determined to save the Agency, or the only place where she can be allowed to live.