Memory lost

Maybe...

• Derailment 
• Lovely Runner (toward the end)
• The Last Princess (in the last third)

and I have a list with amnesia (some might work): https://kisskh.at/list/4q6aXEo1?page=1

Adding some more that haven't been mentioned (including in emeraldarrows' awesome long custom list):

• "Watashi wo Moratte": Tsuioku Hen - FL
• 18 vs. 29 - FL
• Ancient Love Poetry - FL (rebirth like but not exactly rebirth)
• Autumn's Concerto - ML
• Save the Last Dance for Me - ML (2x amnesia, they date after the 1st amnesia)
• Snow Angel - ML (reunited as lovers eh or not? kinda forget but bad ending though)
• Stairway to Heaven - FL (reunited and get married but bad ending though)
• The Innocent Man - FL
• The Prince Who Turns into a Frog - ML (2x amnesia, they date after the 1st amnesia)
• Winter Sonata - ML