Here's how to unlock the 6 different endings. Note: Scenes in Chapter 8 are triggered while traveling with Mayu in the Storehouse, Whisper Bridge, Kiryu Projector Room, and Kiryu-Tachibana Heaven Walkway.

Ending	How to unlock
Crimson Butterfly Ending	Defeat the Bound Man in the Final Chapter in over a minute without having seen the scenes in Chapter 8.
Frozen Butterfly	See all scenes in Chapter 8 and defeat Girl in Bloody Kimono in more than two minutes.
Hellish Abyss Ending	See all scenes in Chapter 8 and defeat Girl in Bloody Kimono in Dark Return with a Fatal Frame shot.
Long Road Home	Go straight through the passageway in Kureha Shrine without chasing Mayu in the Final Chapter OR Unlocked after clearing the game at least once.
Promise Ending	Don't watch the scenes in Chapter 8 and defeat the Bound Man in the Final Chapter in less than a minute.
Shadow Festival Ending	See all scenes in Chapter 8 and take longer than five minutes to defeat the Bound Man.