this manga's takano had several flashbacks which seemed to refer to the grandpa of the takano in higurashi. also higurashi took place in 1983 (30+ years before this one). plus, the community center in this story greatly resembles the one in real life Shirakawa village which was used as a base for the town of Hinamizawa. the village also resembles the real life Shirakawa up to the alluvial fan thing. i'm starting to think hotarubi no tomoru koro ni is a legit spin-off.