Forget Me Not

Dramas focus on memories. One of the leads lose their memories when a specific time frame passes, forgetting who they've previously been intimately involved with. This doesn't disrupt their daily life, but it affects their relationships and ability to connect with others.

Both talks about someone forgetting about the memories they have with their friends.
In the movie "One Week Friends" it talks about a girl who can't remember the memories that she had with her friends, and in "Forget Me Not", it talks about a girl who everyone can't remember of the memories pass with her and who she is

Pretty similar in most respects. A girl with a memory related issue
Both heartbreaking romance and lots of crying

In both movie the boy meets a girl and he falls in love with her at first sight. They start to enjoy happy days together, but than the girl reveals a sad secret...

Okitegami Kyoko is a beautiful private detective who has a deep love for money. She is also known as the Forgetful Detective. Her memory is reset when she sleeps at night, which means she can strictly adhere to confidentiality requirements. She solves all her cases within a day, whatever they may be. She is the world's fastest detective! There is something really important that Kyoko must never forget, and it is written on her body with a magic pen.
“I am Okitegami Kyoko, detective. My memory is reset after one day.”
Meanwhile, even though Kakushidate Yakusuke has a crush on Okitegami Kyoko, he is always mistaken by her as the culprit of a case. No matter how close he gets to Kyoko, she totally forgets about him by the next day.

In which the main character unintentionally forgets about the past.