Human memories can be edited in the future through a new technology. 

Light used to be closed with his father. But he drifts apart from him when he got into a relationship with his girlfriend and addicted to his smartphone. After his father passed away, Light wants to give him the last gift by changing the bad memories he had with him. The system fails to edit his father’s memories, because the truth is his father never had any bad memories of him. He always loves Light and remembers every part of him.