After succeeding in their winter conflict against Taiju Shiba and his Black Dragons, the Tokyo Manji Gang absorbs their group’s remaining members. Due to his heroic courage and indomitable spirit, Takemichi Hanagaki should have accomplished his goal of defeating the tragic fate awaiting his girlfriend, Hinata Tachibana.

In reality, Takemichi’s troubles are far from over. Although Takemichi’s actions have exposed Tetta Kisaki’s treachery, the conniving schemer has found power elsewhere: Tenjiku, a dangerous gang led by the enigmatic Izana Kurokawa. Izana sets his sights on Manjirou “Mikey” Sano, pursuing a vicious interest in the Tokyo Manji Gang’s aloof leader.

In the future, Takemichi discovers that the machinations of Izana and Kisaki led to Mikey’s moral ruin—a downfall that directly results in Hinata’s death. Unfortunately, a terrible loss robs Takemichi of his time-leaping ability, stranding him in the past with one final chance to rescue everyone he loves.

In spite of his best time-leaping efforts, Takemichi Hanagaki continuously fails to prevent the present-day death of Hinata Tachibana, his adolescent love. The adult Takemichi grapples with grief and the ramifications of the Tokyo Manji gang’s criminal empire—an unintended product of his timeline meddling. Though the gang once operated under the idealistic Manjirou “Mikey” Sano, it has now been taken over by the malicious Tetta Kisaki and, as a result, has abandoned its original optimistic intent.

Despite feeling hopeless, Takemichi travels to the past once again to investigate Black Dragon, a rival motorcycle gang whose actions ultimately lead to Hinata’s demise. There, he meets the young Hakkai Shiba, a fellow gang member whose older brother, Taiju, tyrannically rules Black Dragon. When Taiju brutally beats Takemichi in a one-sided street brawl, Hakkai attempts to withdraw from Tokyo Manji in apology—an act that Takemichi must prevent to spare Hakkai a grim future.

Through a shared tragedy, Takemichi bonds with Chifuyu Matsuno, establishing a close comradery both boys desperately need. With Chifuyu on his side, Takemichi works to unravel the fates of Black Dragon’s members, fighting to create a happy future for his loved ones.

Takemichi Hanagaki’s second year of middle school was the highest point in his life. He had respect, a gang of friends he could count on, and even a girlfriend. But that was twelve years ago. Today, he’s a nobody: a washed-up nonentity made fun of by children and always forced to apologize to his younger boss. A sudden news report on the Tokyo Manji Gang’s cruel murder of the only girlfriend he ever had alongside her brother only adds insult to injury. Half a second before a train ends his pitiful life for good, Takemichi flashes back to that same day 12 years ago, when he was still dating Hinata Tachibana.

After being forced to relive the very same day that began his downward spiral, Takemichi meets Hinata’s younger brother. Without thinking, he admits to his seeming death before flashing back to the past. Takemichi urges him to protect his sister before inexplicably returning to the future. Miraculously, he is not dead. Stranger still, the future has changed. It seems as though Takemichi can alter the flow of time. Given the chance to prevent his ex-girlfriend’s tragic death at the hands of the Tokyo Manji Gang, Takemichi decides to fly through time to change the course of the future.

On Christmas Eve, four-year-old Miri Unasaka arrives in Tokyo completely alone, in search of her father. The bright lights and merry atmosphere guide Miri to a big hotel and a man with a delicious-looking cake. However, the child has just unknowingly walked into the center of an elaborate, foolproof plan for assassinating a dangerous mafia boss.

Professional assassins Kazuki Kurusu and Rei Suwa live together, fleeing memories of their grim childhoods and avoiding emotional connections. When their mission goes awry and they end up bringing Miri home, there is only one reasonable thing to do: return Miri to her mother. But the girl’s innocent laugh and pure worldview quickly enamor her to Kazuki, who secretly enjoys playing a parent, and it is not long before Rei’s impenetrable heart makes room for Miri.

Miri’s every move is unpredictable, and Kazuki and Rei find raising an energetic child harder than any of their missions. Although it presents a great risk to their careers, Kazuki and Rei—both assuming the affectionate nickname “papa”—decide to provide Miri with a normal childhood despite all the odds stacked against them.