The Charming Step Mom

In both shows a young female enters a widower's home and takes care of the man's three children. In MMJS, there is an added hidden identity plot point.

the main leads are both bodyguards. There is a fun romance. Now the difference is in bodyguard SAO it;s the female lead who is the bodyguard. Where in the Charming Stepmom its the male lead. I liked both of them, Hint: don't analyze for credibility just enjoy it.

Both require a suspension of disbelief. Both have female leads filling in for a sister in a way that makes no sense. The Charming Step Mom was a little more fun. She's the One also gives vaguely Well Intended Love vibes too.