Both titles involve being kidnapped at a young age and co-habitation which leads to the female lead believing the male lead is a good person.
They both have time travel as the main theme with a mysterious object that helps them travel back to the past. Both of the main characters go back to the past to save someone who died and the setting is based in high school.
Both series are focused on a high school cheerleading team from Japan winning a competition in the USA.
They're part of the same series and go to the same high school. The main characters of Unrequited Love appear in With You (with different a actor and actress).
Our Times and Youth Never Returns are centered around first love school romance. Both involve real life problems that we can all relate to. Joe Chen also stars in both of them.
Want more mind boggling series that gets you hooked on the first episode? SPEC is definitely your next drama to watch. If you like Toda in Liar Game, you'll love her in SPEC.