A 4koma series by Fuukadia (narcolepsy). In it (2nd half) Izayoi Sakuya is tasked to travel to a parallel dimension version of Gensokyo's far past, when the Great Hakurei Barrier was not yet formed, a secret and early-work-in-progress, to supposedly spy for a weakness on Yuyuko. But ultimately she, and others, wind up completely preventing the formation of the Barrier-enclosed Gensokyo with the help of the (1st half) already bumbling, but well-meaning, Four Oni Devas (Oni Big Four of the Mountain). (Ibuki Suika, Hoshiguma Yuugi, Ibaraki Kasen, and, as a "substitute Oni", Konngara)
