The dragon's harem - Chapter 1422: The One Wave

Side story of Kyoukai Senjou no Horizon bundled with the first press release of the 1st, 3rd, 5th and 7th Blu-ray volumes of both seasons of anime.

This side story follows Asama, Kimi and Mitotsudaira aboard Musashi one year before the beginning of the main story, as Asama is considering to create a music band together with her two friends for the next festival in Aki, a territory under the governance of K.P.A. Italia.

This is an alternate history. Decades after the fall of the Eastern Jin Dynasty, the world is still in chaos, although there is hope for reunification.

After an unforeseen circumstance, Kayn is abruptly transported back in time, accompanied by someone he once considered his most significant foe. As he delves deeper into the past, Kayn discovers the truth behind the events that led to his betrayal by both his guild and allies, as well as the agonizing reality of being abandoned by those he was sworn to protect. Fueled by a deep desire for retribution, Kayn vows to take matters into his own hands and right the wrongs of the past, proclaiming his intent to become a Kingmaker and shape the future according to his own vision.

Xu Mo, a modern high school student was sent back in time to Jing Kingdom and found herself trapped inside of the body of a princess with the same name.

She had barely recovered when she learned of an unparalleled fiancé and in a daze, they got married. Then the stunning genius physician who normally does not pay attention clamoured to marry her. After that, there was a cold general, a flirtatious lord, a tsundere young master……

As it turns out, this was a male-dominated dynasty. Because the female population was sparse, the entire nation shared wives regardless of rank or nobility. Is it feasible for someone who wants to maintain monogamy in this dynasty?

- Description from Novelupdates