Complete the game and create a cleared saved game file.
To unlock an alternate ending, collect the following items in the corresponding locations and then complete the game:
ITEM - LOCATION
Water Doll - During Day 1, search the well at the top-right corner.
Forest Earring - During Day 2, search the empty stage in the middle.
Bloom Ring - During Day 3, search the tombstone at the top-right corner.
Crystal Pendant - During Day 4, search the flower next to the top-right statue.
Sunny Dress - During Day 5, search the blue chest on the second floor.
Love Tiara - during Day 6, search the belt in the church.