a ghost story he didn't like the ending of.... It's also interesting to see that Andou is explicitly the in-universe protagonist of the town. It makes her the character who is meant to experience all the ghosts stories first hand. But she's been barred from doing so before the timeloop even started.
All before our protagonist Sakura entered the equation, and became the out-of-universe protagonist of the story we're reading. Considering then that the town is Hisagi's creation, would Sakura be a legitimate outside force then? while her parents are from here she herself isn't.
Hisagi's is providing the spectres but the loops, The town itself, and presumably Andou's resurrections are all being handled by Oiya-sama. there's also the fact that Oiya-sama is genuinely otherworldy in behaviour while this guy walked up went "yeah I'm that famous author and also I ascended and am still a pretty normal guy" I'm sure there's more we'll find out later, but I dunno it's like he stumbled on Oiya-sama's domain and basically just hijacked it for his own ends.