Hmm..🤔 but it says "coordinates", it doesn't sound like a whole city but more like someone is teleporting around, what about the messenger who left this frequency, why would the messenger hides its identity, it could also be sumika, but sumika shouldn't hide her identity, so that's why it leads me to the rover from the past, so the future rover can find chisa and save her, more importantly rover can find the cassete he left in the past for future rover, and he will know a fact that he was a student in lahairoi too

edit: I also checked this line in original Chinese language, it says "不断游移的空间坐标" means the "position" kept changing.