The plots are very similar. In my perfect stranger, the ML wants to find the cause of his death, so it's got a bit of suspense element added to it. In twinkling watermelon, the plot is more about bonding and making sure the family sticks together. Both have romantic stories going on both in the past as well as future selves.

Similar Vibes
? ML working in an intense job (one being news anchorand other being Planning team)
? Both ML had a connection to FL in past
? Both being kinda memory related due to an incident (one sees future and one remembers everything)