Nearly twenty years into the 21st century, people have forgotten the existence of youkai. When a number of unexplainable phenomena plague adults of the human world with confusion and chaos, thirteen-year-old Mana writes a letter to the Youkai Post in search of answers, only to be greeted by Gegege no Kitarou... (Source: Crunchyroll)

For over a century and a half, two interstellar states have wrested for control of the Milky Way. The Galactic Empire, an absolute monarchy ruled by Kaiser Friedrich IV and an entrenched nobility, seeks to suppress the rebels daring to oppose the inviolable crown. The Free Planets Alliance, a representative democracy led by a corrupt High Council, degenerates as its elected leaders⁠ use war and conflict as a way to win popular support. But this long-standing stalemate between the Empire and the Alliance ends with the rise of two opposing military geniuses. Reinhard von Lohengramm, a minor noble and High Admiral of the Empire through his strategic brilliance and his sister's position as the favored concubine of the Kaiser, dreams of conquering the galaxy and uniting mankind under his iron fist. Meanwhile, Yang Wen-li of the Alliance, an avid historian and reluctant commodore hailed as the Hero of El Facil, uses his tactical prowess to navigate around his leaders' incompetence—and to carve the path to lasting peace. As the war rages on, Reinhard and Yang each strive for their ideals and to secure their place among the stars as the leaders of a new era of galactic heroes.

Following the temporary retreat of the Altana Liberation Army from the Kabuki District, the state of the war has seemingly improved. However, as the Oniwaban, Shinsengumi, and residents of the district combat the army's remnants, Edo's greatest inventor Gengai Hiraga is abducted. Responsible for causing the enemy's withdrawal by rendering their weapons useless, Gengai's nanomachine virus is now at risk of being shut down. Meanwhile, a laser capable of obliterating a planet is activated in Earth's orbit on the Liberation Army's mother ship. Another battle ensues when Shinsuke Takasugi and the rest of the Kiheitai arrive on the vessel to stop the weapon from firing. Forced to fight a war on two fronts, the Yorozuya and their allies must prevail on both sides to save Edo and the rest of the world.

After the fierce battle on Rakuyou, the untold past and true goal of the immortal Naraku leader, Utsuro, are finally revealed. By corrupting the Altana reserves of several planets, Utsuro has successfully triggered the intervention of the Tendoshuu’s greatest enemy: the Altana Liberation Army. With Earth as the main battleground in this interplanetary war, Utsuro's master plan to destroy the planet—and himself—is nearly complete. An attack on the O-Edo Central Terminal marks the beginning of the final battle to take back the land of the samurai. With the Yorozuya nowhere in sight, the bakufu all but collapsed, and the Shogun missing, the people are left completely helpless as the Liberation Army begins pillaging Edo in the name of freeing them from the Tendoshuu's rule. Caught in the crossfire between two equally imposing forces, can Gintoki, Kagura, Shinpachi, and the former students of Shouyou Yoshida put aside their differences and unite their allies to protect what they hold dear?