Perhaps this is a niche adult anime. I'll search for the title on anidb. it's not indexed. Let's search for "Shinseki no 18-Sai" on Wikipedia..
In the end, the phrase is a linguistic ghost—a fragment of Japanese half-remembered, half-invented, chasing the echo of a dub for a show that lives only in our collective desire for more cozy, slightly awkward overnight-stay anime. shinseki no ko to o tomari da kara english dub work
The anime community has seen this phenomenon before. A fan watches a show raw or with poor subtitles, misremembers the Japanese title, and then searches for a non-existent English dub. Perhaps this is a niche adult anime
Noah nodded. He had been a stage actor once; his voice was flexible in a way their indie studio needed. Maya cued the first line. Noah lowered his voice so it trembled just slightly — a thread of wonder braided with a shiver. Let's search for "Shinseki no 18-Sai" on Wikipedia