This likely refers to the release group or source tag (possibly Anime7 or a similar encoder) responsible for distributing the "Raw" (unsubtitled) version of the episode.
The episode features Special Week and Tsurumaru Tsuyoshi being "trapped" in a classroom by Gold Ship, who communicates through a manekineko (beckoning cat statue) and forces them to use teamwork to escape. Technical Context A7 Umayuru 19 Raw.mkv
This indicates the file is a high-quality Matroska video container containing the original Japanese broadcast without hardcoded English subtitles. This likely refers to the release group or
was originally released as a web anime series on the official Umamusume YouTube channel between October 2022 and March 2023. Anime/Umayuru | Umamusume Wiki | Fandom A7 Umayuru 19 Raw.mkv