One of the few older dramas that are aging like fine wine thanks to a director that utilizes cinematographic storytelling and stellar acting that will make you feel their emotions. There are no filler episodes and it has a good pace.

I could not help but to compare this drama with "Lighter & Princess" as it has a very similar story but goes much deeper and strays away from being an idol drama.
This section of the review is best read if you have seen L&P since I am comparing the two.

Similarities:
- College Sweethearts with a sheltered but strong FL and a popular ML - he beats someone up after being betrayed by said person, goes to prison, doesn't tell the FL but rather disappears and then comes back many years later and so the story goes.

Differences:
L&P leads are programmers, WTLOG leads are artists (drawing comics, oil paintings, etc). L&P is 36 episodes and an idol romantic drama, WTLOG is 24 episodes and a romantic melodrama (as in the ML shows vulnerability & complex emotions, which in c-dramaland apparently means melo(?)... no need to fear crazy parents in law, amnesia, slapping , etc.) but it does carry a darker, more realistic tone.

The main difference is the ML & the relationship, which in L&P was quite toxic in my opinion as the FL did all the work in the relationship and he wasn't really much different in terms of personality (aloof) before vs after prison, but the ML here was flirty and bubbly before and visibly broken inside afterwards. His reason for prison was also more severe.
More on that under "about the ML"

-------------- (actual review)--------------
It has really good cinematography / story telling, that reminds me of film and it uses a lot of wide shots with the environment symbolizing what's going on without using words. Example: they part ways on a seemingly normal day, one person going down the stairs and one going up as a way to symbolize how their lives are going to change.
Although it was made in 2017, it actually holds up quite nicely quality wise, also thanks to live audio recording (no dubbing is always a plus).
I liked that each episode had a poetic title that would be reflected on at some point throughout the episode. At the end of some episodes there was a deep question left for the audience . I really liked that.

The FL is calm, kind, strong and all in all very real. She is anything but a damsel-in-distress and cares for the people she loves. There is nothing negative I could say about her to be honest. The leads also have very good, natural chemistry that makes it easy to believe their story.

But the real star of the show was the male lead. I was really impressed by Fan Si Qi's acting, who is one of THE most underrated idols turned actors of c-drama land, he makes you believe that he is actually the character and offers a wide range of emotions. FSQ can act with his eyes (if this makes sense) and his character made me teary eyed in multiple occasions. + he's a good kisser and a good crier.

About the ML (spoilers!!):
Xiang Ze Yi was a flirty and fun art student, who was always up to shenanigans with a smile on his face and capable of showing emotions. It's very much a male-chases-female-first story and they are super adorable as a couple. He's the ideal type of first love and potential life partner, someone who makes you feel special and loved.
But when life had different plans and he came back as an ex-convict a decade later, he changed a lot. This is where I also saw a big difference between L&P and this drama. Maybe it's the melo part after all - but life forced him to change. In his heart he was still that flirty and fun college student but the consequences of his actions not only put him in prison but also took away all of his prospects of a future. He smokes, has a bit of a beard and is living quietly. It doesn't take much for him to shed a tear and he is visibly in pain over the past.
L&P ML was building a life for himself after prison but the Ze Yi always wanted to return to his love. There are many good quotes and it was painful but also poetic in a way to see how life can break a persons' spirit. But I also want to say that he was never weak or whiny, full credit goes to the actor and writer here because they found the perfect balance that made him seem very vulnerable but also well aware of his situation and wanting to re-connect with the FL.
I found him quite realistic, more than many other drama MLs, he didn't turn cold after what happened to him - after all he is human and humans have emotions. The stone cold ML characters we often see in dramas tend to have a sad background story that made them like this but Ze Yi went into hiding mode, all too aware of his own pain. There were many heart wrenching scenes when he was by himself. But enough of the spoilers! There is happiness and healing too. I just cannot put into words how much I enjoyed the unfolding of his story and the actors' portrayal of complex emotions, pain and healing.

The past is the past but it's painful nonetheless.

The cons:
The story might not draw you in right away since the first half of the drama the story goes back and forth between college days and present, which can be confusing in the beginning since they don't tell you clearly and you kind of have to figure it out.
The college days are cute but a bit average, it gets more interesting once the time skip is explained, so don't give up ;)
It does have a few minor plot holes but nothing that bothered me too much or that stayed for long. I thought one character's comeback was unnecessary and quite unrealistic but said person disappears again soon after so it's only a minor inconvenience. Same goes for the love triangle if you can even call it that - quite frankly the story of the ML was so intriguing that I barely paid attention to the SML and neither did the story.
The other couples in this dramas and the work side were okay but not that memorable.

Ending (spoilers, do not read if you have not watched it yet!)

At first I thought it was a perfect happy ending... but as I was writing this review, it also reminded me of The Forbidden Flowers' ending. Nowhere near as tragic but you could potentially see the ending two ways. It's happy but their last dialogue does make me wonder if it was an illusion...

CONCLUSION
A beautiful and sad but underrated drama that trumps L&P in my opinion, and left a lasting impression on me. It's release date may have been long ago but it will be in my Top10 dramas this year. If you want to see really good, emotional acting of a ML and pretty story telling without watching an absurd amount of episodes - this drama is for you. :)