My favourite thing about the sealed esoteric history is that it's kind of an alternate perspective on some of the Hifuu club activities. Like, I could 100% see everything that occurs within the anime happening in the actual canon, but it isn't depicted. It's a perspective a lot of doujin stuff goes for WITHIN Gensokyo but I rarely see in the context of the hifuu stuff, that's usually tellings of how Merry becomes Yukari or just RenMerry SoL