Amusement Park Arc

This is the first story arc of the Sakamoto Days series, spanning the manga's opening fifteen chapters across its first two volumes and adapted as the anime's initial five episodes. It establishes Taro Sakamoto, once hailed as the world's finest hitman and now a shopkeeper, husband, and father, alongside his family and the allies who gather around him. When a colossal bounty lands on his head, a simple family day out at an amusement park turns into a running battle against assassins.

Taro Sakamoto, once celebrated as the deadliest hitman alive, now runs a corner store and lives quietly as a husband and father to Aoi and Hana. His calm breaks when Shin, his former underworld partner and a mind-reading clairvoyant, arrives hoping to lure him back into contract killing. When Sakamoto refuses, Shin is ordered to end him for abandoning the trade, yet he loses badly and ends up begging the Dondenkai men to spare his old friend. Sakamoto steps in, clears out the attackers with ease, and Shin stays on to work behind the counter.

The days that follow bring a parade of new faces, including the former Triad heiress Lu Shaotang, until Sakamoto's old associate Nagumo appears to announce that a one-billion-yen bounty now hangs over his head. Hoping for an ordinary outing, Sakamoto takes Shin, Lu, and his family to an amusement park, but killers crash the trip to claim the prize. Shin, backed by Sakamoto, downs a poison user, and the pair then run into the far deadlier Boiled and Obiguro.

Lu manages to hold Obiguro at bay while Sakamoto, at first outmatched by Boiled, sheds his bulk into his lean fighting form and overpowers him. Despite their care, Aoi learns of the bounty, and the ordeal convinces Sakamoto and Shin to strike at whoever placed it rather than fend off attackers forever.

The arc lays the series' foundation, gathering Sakamoto, Shin, and Lu under one roof as the latter two take up work at the store. The staggering price on his head reshapes Sakamoto's daily life, forcing him to reveal his slimmed-down combat form and put its full power on display against Boiled.

Several pillars of the wider world surface here as well. The Dondenkai and the elite killers Boiled and Obiguro make their entrances, Lu's combat pedigree is confirmed, and passing references establish both the Order, which Sakamoto once belonged to, and the JCC. With Aoi now aware of the danger, Sakamoto and Shin resolve to trace the bounty to its source, steering the story toward the Lab Arc.