Because It's the First Time (2015)

Both dramas involve childhood friendship and a love triangle. These dramas depict youth, life and friendship. The two dramas have adorable female leads! "Because It's the First Time" is a quality drama you shouldn't miss.

Because It's The First Time is also about the life of university students, twenty-some boys and girls. It shows the same problems like money (part time jobs), love life, family (dead or divorced parents). The only difference is, the main characters in Age of Youth are only girls.

They actually have the same story and My First First Love may actually be the remake of Because It's The First Time!

These two have the same "team of close friends" vibe.
Shut Up may have more depth though.

Both about youth, friendship and rooftops!
Hit the Top is more about achieving dreams (and time travels), while BITFT it's about overcoming hardships.
plus, both starred Kim Min Jae