A drama that combined live action and animation and they're synergizes well.
The live action isn't much dramatization, the animation that is represented by cells in Yumi's head explains a lot of things that are turbulent within Yumi in many ways that make sense and makes me think "oh this is what happens inside my head, when I see Yumi experience something."

The story of this drama is simple, about Yumi who goes about her daily life, goes to work, meets love, etc. but accompanied by the cells that work in Yumi's head, they try their best to help Yumi live a happy life, making this drama very exciting. The execution is good, the acting is good, I just really think this drama is good, especially when things start to get serious in Yumi and Woong's relationship, they're cute together and got a lot of dokidoki moments between them but the dynamics in their relationship feels organic.

The last two episodes is hard to watch for me, Yumi and Woong already spent to much time together, create a lot of memories together, the way they did it with that card gimmick and flashback, it broke me.

Oh yeah, the OST are also good, really helps to amplify the feelings and emotions in every scene. My favorite is "Our Story" by Melomance, they slayed with "Love, Maybe" this year in Business Proposal, and both songs affect me in the same way, that I will only take in the good memories between Yumi and Woong, like I did with Shin Ha Ri and Kang Tae Moo. I still can't move on from Business Proposal.

I don't know if I'm going to watch the 2nd season, I love Yumi and Woong too much. So yeah, 5-stars from me, thank you.