Judging by the theme and mood in the image of Jimin, it gives off sad vibes which actually matches the plot. The extra photo seems unnecessary and there is no Author's name. The blurring effect makes the cover less eye-catching.
Title: 4/05
The title is common and simple but as we read the story, it gives very deep value and meaning to it.
Synopsis: 8/10
The blurb isn't long nor short, it's a summary of an important part which does reveal about the plot, both main character's personality and later on causes the climax in the story so it's a good cliffhanger as well. The description was attention-grabbing and hit the interest inside me.
Execution: 5/10
Events and incidents that kept the storyline balanced and connected with one another, or should I say every aspect of the book is great except for the things I have mentioned in the review.
Plot: 13/20
The plot is very thrilling and praiseworthy. The karma plot twist was too shocking. I love how you added the 3 years past scenes along with the present. Some of the things were rushed at first, most of the things were left unexplained. Yejin knowing most of the things about Jihoon out of nowhere is unsettling. The source of information known to the characters but unknown to readers at once is okay but repeating this many times makes them lose interest. One of the examples is how she knew Jungkook interacted with Jihoon when she only met him at the library for the first time. Readers prefer showing more than dictating and Yejin mostly dictates such infos in her thoughts.
Writing Style: 9/20
Your writing style is good, but in early chapters most of the dialogues are without action tag or good description of mood. Their feelings were delivered through the dialogues and it made me imagine them talking with blank faces. If you read Yoora's first call again, you will notice. Also I suggest adding more explainable details of place, appearance, feelings and action without repeating the same sentence twice in different or similar ways because it gets cliche. Small example: "For now, I have warned you for now" (Chapter 9)
I will show you one more paragraph that have a writing mistake "They all were laughing from watching Hana's frustrated look. Soon she gets a call, as soon as she saw the caller ID her smile disappears" (Chapter 9 again) If she was already frustrated, she didn't smile or did she?
Grammar & Vocabulary: 5/20
I pointed out only a few mistakes, I hope you re-edit all of them too which I didn't mention here.
