For anyone that’s beaten the miniboss in Ashina Reservoir: https://waypoint.vice.com/en_us/article/vbwkjd/15-hours-in-sekiro-gave-me-a-midterm-exam-that-exposed-my-whole-ass
I don’t recommend banging your head against this wall because the real mid-term exam comes a few hours later with one of the main boss fights in the story.