After stopping a fatal battle with Hajime Saito, a top government official asks Kenshin's help in killing a shadowy assassin who's threatening the future of the regime.

Kenshin's final effort to win the ultimate battle ends with Shishio destroying himself. But in the wake of Kenshin's victory, Shishio's closest aide vows revenge.

This is the story of how Kenshin came under the wing of Soujiro Hiko the 13th, and how Kenshin became a manslayer.

Act 4 is about the betrayal against Kenshin, how he lived for the next few years as a manslayer, and the origin of his cross-shaped scar.