it's one of those dramas that you just don't want to end. A sweet story about love, uni, friendship, and lots of food.
I couldn't get into this last year when I tried watching Weightlifting Fairy Kim Bok Joo right after finishing Start-Up! I really didn't like Nam Joo Hyuk character in that show and so didn't gel with this one.
Thankfully, however, Twenty-Five, Twenty-One changed all that and I'm so glad I revisited this show.

Firstly, our protagonist (Kim Bok Joo) played by the wonderful Lee Sung Kyung is so adorable that you can't not fall in love with her. Her story was lovely - finding out that she's a woman and not just a weightlifter, will resonate with a lot of people.
Joon Hyeong's character works so well with her too and you get why Nam Joo Hyuk is such a good actor.

I don't want to spoil it for you but will say to just go and watch it. Enjoy its purity and have fun!