"Goodbye, Eri" is the name of the 200-page manga. Manga Plus explains the plot this way:
"Yuta uses his phone to record his mother's final days as she passes away. Yuta goes to the hospital's roof to commit suicide after she dies, but a chance encounter with a mysterious girl leads him down the path of producing a film."
Shonen Jump Plus is a good place to go if you want to read it in Japanese.
Fujimoto's recent work includes a one-shot manga titled Look Back, which is also getting a TV anime adaptation this year.