I won’t repeat some of the comments made by other reviewers.
I remember on line that was made “if reset was to happen, then not everything will go back to as it should be.. because we have come too far.” This is not an exact quote.
So using the line above, Tae hi and lieutenant did not disappear and end up meeting again in 2020.
The other mom who did not die .. I wonder what happened to them. Perhaps they are living happily in an another dimension.
This is the only way I can Rest In Peace with this bizarre ending.

However, I am glad I watched it..it was engaging and intriguing till the end.