Shinseki no Ko to Otomari Dakara (親戚の子とお泊まりだから) is an adult-oriented (H-anime) OVA series, often discussed in niche communities under various "exclusive" labels like "Kara Exclusive" or "Studios Dakara".
For more specific "Kara Exclusive" details, users often look toward dedicated forums such as the Kara no Shoujo Wiki for related visual novel styles or community groups like Shinseki No Ko To O Tomari Dakara Studios on Facebook for fan-driven updates. character's backstory Shinseki No Ko To O Tomari Dakara Studios : dry-goods shinseki no ko to o tomari personajes de kara exclusive
So a plausible interpretation:
"A sleepover with my relative's child — exclusive characters from Kara" Not commercially published, thus no official character list
Be warned: Kara Exclusive’s DRM tied characters to real-time sleep data – so some “personajes” (characters) may never be fully recovered. Not commercially published
As the keyword suggests, these characters are exclusive — meaning they have never appeared in a public release. However, dedicated fans have claimed to “encounter” them under specific conditions: