Twelve Letters

Very different plots, similar characters/main relationship. Both dramas have two lonely, poor, and damaged leads - a FL struggling with issues with her family and an orphan ML who works hard jobs - who become each others' family.

Both Twelve Letters and Yesterday Once More have that same bittersweet, nostalgic feeling. They’re not just about love, but about how time changes people and relationships. In both, the romance isn’t straightforward; it’s tender but marked by distance, regrets, and missed chances. They focus on memory, growth, and the way small moments stick with you over the years. The tone is slow, emotional, and reflective, making you think about your own past and the “what ifs” in life.

Both shows feature the younger generation heavily involved in uncovering or altering the tragic timelines of their parents (or parental figures). Both uses dual timelines, In "My perfect stranger" the daughter time travels into her parent's past timeline.
Both features the suspense and mystery elements as catalysts for the plot and MPS shows less traumatic events compared to TL with solid happy ending.

Both are about two damaged kids who make each other their only family. Both MLs feel they have no future but the FL does and sacrifice a lot for her. Both FLs fiercly love the ML. Both dramas have a gritty, serious, and realistic feel.