You can find more details regarding the cast and production history on platforms like The Movie Database (TMDB) character analysis of Nanashi and Hitomi, or would you like a summary of the later episodes (3 and 4)? Boku ni Sexfriend ga Dekita Riyuu (2022) - TMDB

Provide a of their major romantic milestones.

The title translates directly to "The Reason I Got a Sex Friend." In the landscape of adult visual novels, manga, and OVAs, the "Sexfriend" (セフレ) trope has become a staple of early 2020s doujinshi and indie animation. Unlike a traditional romantic comedy (rom-com) where the goal is confession and dating, the "Sexfriend" narrative subverts expectations by starting after the physical relationship begins.