The criminal organization Port Mafia.

And Dazai Osamu, the youngest executive in Port Mafia history. He attained the rank of executive at the mere age of barely sixteen.

However, Dazai Osamu's inner self was trapped in a state of profound emptiness and nihilism, unable to find a reason for living.

Then there was Oda Sakunosuke, a low-ranking member. Despite possessing incredible skills, Oda remained at the bottom by his own choice (his vow never to kill).

Dazai Osamu saw through to the essence of Oda Sakunosuke, whom everyone else feared—the purity of a man who stopped harming others to become a novelist. Oda Sakunosuke was also the only one who recognized and accepted the "loneliness and void of a crying child" hidden behind Dazai's genius.

That was the beginning.

To Dazai Osamu, Oda Sakunosuke was the only companion he truly connected with in the darkness.

The time the two spent drinking together at Bar Lupin, a quiet bar in Ginza, was the only sanctuary where Dazai Osamu was purely happy in his entire life.

The relationship between the two contains a sadness like parallel lines that can never meet. Dazai Osamu wanted to stay by Oda Sakunosuke's side and emulate his way of life, hoping that through him, he might eventually find the value of living.

On the other hand, Oda Sakunosuke knew that Dazai Osamu could not escape his emptiness, yet he hoped Dazai would not lose his way in the darkness forever.

Paradoxically, Dazai Osamu moved desperately to protect Oda Sakunosuke, but he could not prevent Oda's tragic death.

Dazai Osamu remembers Oda Sakunosuke's last words.

Oda Sakunosuke said: "Whether you live in the darkness or the light, the reason for living you expect will not appear. You know that yourself. ...So, at least become a person who saves people. If both are equally worthless, be a good man. Save the weak and protect the orphans."

These last words became more than just advice to Dazai Osamu; they became a milestone for his life and an absolute spell of salvation.

To Dazai Osamu, Oda Sakunosuke was the only light of his life and an object of eternal longing—the one who pulled him out of the swamp of endless nihilism and allowed him to walk toward the world of light with a human heart.

And finally, Dazai Osamu lived on, missing Oda Sakunosuke.

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However, one day, Dazai arrived in a parallel world.

In this world line, Dazai Osamu discovered that Oda Sakunosuke is alive.

Yet, because only Dazai Osamu possesses the memories of Oda Sakunosuke, Oda Sakunosuke does not think deeply of Dazai Osamu.

Dazai Osamu becomes the Boss of the Port Mafia himself to create a future where Oda Sakunosuke survives and writes novels.

He finally reunites with Oda Sakunosuke at Bar Lupin, but Oda Sakunosuke treats Dazai Osamu only as the Boss and remains on guard.

Seeing Oda Sakunosuke, who does not remember him and treats him with hostility, Dazai Osamu feels a heartbreaking sadness, yet he thinks that as long as Oda Sakunosuke can breathe and write, his own life and being hated do not matter.