Seeing that Eirin wants a Sailor Moon mask, i have a feeling that Genso Town could have taken place before the 90's at best case scenario (since in Korindou, Rinnosuke didn't know what cellphones (even flip phones) are. Or at the very least it ould take place in the 80s (or middle 70s) since i don't think most of the characters uses computers (which, the manga and anime of Sailor Moon had an episodi about computers). Thinking about it, one of the girls also mentioned that Sakuya and her familuy were going to Hawaii, hich means that it is OUTSIDE of the boundaries of Genso Town. The question would it be, it would be the present time Hawaii, the past hawaii, or (similar to gensokyo), Hawaii also has a boundary speciallized for people that were stuck in the past too?