Amnesia Shows & Movies

[P] - After his surgery, Ren Guang Xi forgets his past lover.

[P] - Ghost Kim Hyun Ji does not remember what happened before her 'death'. When she comes back, she forgets her time with Park Bong Pal.

[NP] - Almost everyone in the losing world seems to forget the players who enter the game. (found in Ep. 1 & 9)

[P] - Sento does not remember his pass life, but as he works more with his team, his past life is revealed (part of a series).

[NP] - Poppy forgets her time with the team.

[P] - "People are always greedy for things they don't have, forget to cherish what you already have. They will only realize the cost when it's too late." Lin Xiao Xi has to choose between being skinny and losing something she cherishes. When she chose wrong, her childhood friend, Han Bing, forgets who she is. (found at the end)

[P] - A tragic love story between a couple is ruined due to the mistake of 634 Regina. To protect someone he loves, Oh Soo Min, the male lead, requests to erase his memories. However, his lover's memories, Ham Eun Ho, will have to go too. They part in their own ways and continue with life. Soon, they will meet once again, strangers. (found in Ep. 1-9 & 13-16)

[P] - Ga Mo Tak does not remember his past. Little did he know, his past has a connection with the new counter. 

Also, to protect their identities as counters, they have to erase people's memories.

[NP] - Wei Wuxian does not really get amnesia. However, he is such a forgetful man. I don't want to say which episodes this is apparent in because this trait is just part of his character. You'll just have to watch to know what I'm talking about.