For fans of the Danmachi franchise, this is an excellent side story, right up there with others such as Astrea Record. Originally an event story that was debuted in the now End-of-Service gacha game Danmachi: Memoria Freese (or DanMemo for short), it is one of several popular stories to have emerged from the now-dead game that Omori picked up and adapted into light-novel format. In particular, this side story focuses on the ancient tale of Argonaut, the Hero of the Beginning, the inspiration for so many heroes of old as well as today, whose impact is still referenced and seen in both the main story of Danmachias well as Sword Oratoria.
The characters are excellent, vividly painted, and though some may not like the exaggerated and melodramatic tone/prose at times, it suits the type of tale the author means to tell. Omori successfully weaves a tale that riffs off of popular stories from all over the world, including the tale of Theseus and Ariadne from Greek myth, references to Don Quixote, and such in order to create a unique myth that belongs to Danmachi alone. It is not as innocent as the synopsis and references to it may suggest, but weaves a beautiful message in between an epic tale that reflects on the story of Danmachi thus far as well as hinting towards potential future developments in the main series.

In my opinion, a must read for any dedicated fan of the franchise, and an all-around good experience. Now if only they released official English/other language translations.