MTL - From the Dungeon, Slaughter the Demon Apostle - Chapter 668 the key to this

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.

Once upon a time, the Land of Promise thrived under the cycle of the four seasons change. Until a vengeful enchantress cursed the land, and divided it into four realms each with a ruler to bear its burden.The people suffered for years under the endless heat in the Summerlands, the bitter cold in the Winterlands, the never changing bloom in the Springlands and the constant fall in the Autumlands.A prophecy whispers of a marriage between a king and queen that will release the land from its curse and unite it under a single kingdom.Princess Caroline is forced to marry the Summer King, will she be able to fight for a peace amidst a court full of power hungry nobles and will she succumb to a burning love in the arms of a fiery warlord?

Akun, along with his classmates, was summoned as heroes by a goddess to save the world from the demon king. Akun, doubting he has what it takes to save the world, asks the goddess to send him back. Little did he know that this request infuriated the goddess. “How dare a mere mortal go against my will,” she thought to herself while maintaining her facade. She opens a portal for him to go back. Little did he know, the goddess had something else in store for him. As he passed through the portal, his soul was separated from his body, and he fell through the sky and earth until he landed in the body of an ant in the godforsaken forest. Left there to die by the hands of the goddess, Akun awakens the “Endless Evolution System.” [Ding!! The Endless Evolution System has been activated!! Grind to gain evolution points and evolve yourself and your comrades!!] “Endless Evolution System? Evolution points?” “Does this mean there’s more to my transformation? Can I evolve even as an ant?” [Ding!! Unique skill detected!! Skill: Super Gamer Shop!! Evolution points can also be used on this skill to buy items!!] Follow Akun on his new epic adventure, and find out exactly what awaits him, maybe some conquest and retribution.