German culture also has Übernachtungen bei Verwandten, but the phrasing would be less indirect. A German might simply say: "Ich schlafe bei meiner Nichte / meinem Cousin."
So the whole string seems like a broken search query or mnemonic, maybe someone tried to say: German culture also has Übernachtungen bei Verwandten, but
Here’s a breakdown:
A relative’s child (often a cousin). To (と): With. Otomari (お泊まり): A sleepover or staying the night. Dakara (だから): Because / Therefore. Otomari (お泊まり): A sleepover or staying the night
Given the specificity of your query, here are a few educated guesses about what "Shinseki no Ko to O Tomari Dakara de Na" could relate to: German culture also has Übernachtungen bei Verwandten, but
The phrase closely resembles a combination of two key concepts within Oshi no Ko :
I notice you've requested an essay on the phrase with the note "Übersetzung exclusive" (German for "translation exclusive").