They don't seem to be around, so either they've passed or they're deadbeats. The fact that Joe was considering leaving her behind at all suggests that she does have other family in Japan, though.
Maybe not deadbeats, but workaholics that are never home. Seems more likely to me.
can someone help im looking for this manga that im not sure is here bc i read it on mangadex, but its was yuri or shoujo ai. its about this girl who can see ghosts and bc of that she outcasted herself away from ppl but then one of her classmates who was an idol died and she sees her and eventually became a fan and sort of friend even if the idol girl doesnt know she sees her. and thanks to the idol, the mc is able to make friends too and even eventually forms a friend group (one of them also being a fan of the group the dead idol belonged to)