For the specific "WEBRip" release you mentioned, subtitle files (.srt) are often hosted on community databases. Note that these are unofficial and may vary in translation quality: Film Review: My Broken Mariko (2022) by Yuki Tanada - IMDb
The story follows Tomoyo Shiino, an office worker who discovers her best friend, Mariko, has committed suicide. In a final act of devotion, Tomoyo steals Mariko's ashes from her abusive family to take her on one last journey to the sea—a trip they never got to take together while Mariko was alive.
Available for purchase or rent in certain territories. Community & External Subtitle Files
To ensure high-quality and accurately timed subtitles, it is best to use official streaming services:
The film is available on Netflix in several regions with multi-language subtitle options.