(Japanese: 親戚の子とお泊まりだから出れないわ upd)
If you can provide the or clarify what “upd” refers to (e.g., an update to a story, a correction request, a social media post), I can give a more precise informative piece. shinseki no ko to o tomari dakara de na wa upd
The phrase you provided translates from Japanese to: "Because I'm staying over with my relative's kid, I won't be online [or won't answer the phone]. Updated." an update to a story
If we assume this is a corrupted version of a known Japanese title, here are candidates: a correction request