iris

Both are time-travel and mystery dramas with a dash of romance.
Both include the death of a main character and another character trying to save their life.

In both of the dramas, the leads go from forcibly hanging out with each other because their parents are family friends to eventually becoming romantic partners

It's a similar youth drama

another time-travel romance drama where a teenage girl travels back in time and falls in love with not a king but a young lord in this one. it is also adorable like this drama and the story is well-written.

It's been a while since I watched RIABB so I don't really remember the details but there was a wedding.
And then the leads did cohabitate together for a while.
And there's also the discovering one's passion part.

Both start with the cancellation of a marriage.
Both have the cohabitation trope.
Yugure ni, Te wo Tsunagu is kind of like a modernized Long Vacation.

Both of these are high school romance dramas.
They both become close because they are desk mates.

• bubbly female lead & "cold" male lead

In both shows, the female leads "fool" the male leads by using false identities.
Both dramas are romantic comedies with sweet female leads and calm & understanding male leads.