Demon Slayer -Kimetsu no Yaiba- The Hinokami Chronicles

There are 53 total memories available, most are unlocked by collecting through the exploration areas (check the map each area as all are shown), the rest are earned on completion of chapters. They also only unlock to view after the chapter is completed so the earliest you can view 50 is after finishing the main storyline.
Note you have to watch the 50, not just have them unlocked though that can be sped up by starting and skipping the video.