Potential spoilers ahead!
As it turned out, the crime suspense aspect was more of a backdrop rather than the main theme. Even the title hardly figured in the entire storyline other than the beginning and the end of the story so it made me wonder if the scriptwriter had suddenly remembered the trunk and deliberately mentioned it again towards the end. Much as I could see why there was a need to refer to the trunk for the romance aspect of the story, the way it was slotted in felt somewhat unnatural. Moreover, the process to solve the murder case wasn't that engaging nor challenging so it did feel a bit underwhelming. If you are intending to watch this solely for the suspense, you might be disappointed in this regard.
While I usually shun love stories in case they get overly unrealistic, cringey or sweet, the romance in this drama was surprisingly grounded in reality despite the far-fetched and extreme settings. Having a company specialising in brokering fake spouses on short-term contracts, an ex-wife arranging such a marriage for her ex-husband with ill intentions, an ex-husband accepting his ex-wife's "kind" gesture begrudgingly or a woman becoming the rental wife for multiple men while pining for her missing ex-fiance - these are interesting premises but unlikely to see in real life. However, the depiction of what went right and wrong for the key characters in their love lives wasn't unimaginable and at times quite relatable. The downside to being so detailed and emotional at times was that the pace of the developments may be a bit too slow to stomach for the impatient.
If not for the fact that the leads were Gong and Seo, I think I might not have finished this or liked the story. While the crime suspense part of the story didn't wow me, their acting and great chemistry on screen made the romance a lot more bearable and very enjoyable to observe from the sidelines. To be honest, I don't think that Jeong-won and In-ji were necessarily the perfect match for each other but the fact that they had some history between them way before the arranged marriage probably helped to create this impression that destiny was at play here. And since they were in an emotionally-detached state at first, they didn't see each other as romantic partners and began interacting as housemates to become soulmates and romantic partners. Perhaps this progression path was what helped them to connect more naturally and gradually as compared to Jeong-won and Seo-yeon who probably started off on the wrong footing. That partners-in-crime thing when they were kids or that they were leeching off each other to feel more complete just felt wrong in many ways.
I also liked the fact that there wasn't a standard formula-type of happy ending because it was definitely for the better that their characters Jeong-won and In-ji had to deal with their own issues and live well first before embarking on the next relationship. At the very least, the story dangled the possibility of them being together in future so there is still some room for imagination for those hoping for happily-ever-after.
On the other hand, Jeong-won's relationship with his ex-wife Seo-yeon provided a lot of highly-charged angst and drama because they were essentially two flawed and broken people trying to seek fulfillment from each other albeit unsuccessfully. The issue was, they never seemed to connect emotionally so they couldn't come clean with each other on what they wanted or could provide to the other party. It might have been easy to blame Seo-yeon at first for her drastic behaviour but Jeong-won also had a part to play in driving her to the extreme. One thing led to another so it became difficult to say who was more at fault in the end. Conversely, Jeong-won's obsession and clinging onto Seo-yeon even after the divorce was largely due to his personal insecurity and childhood trauma although she also fanned his insecurity with her actions. They both needed to get away from each other in this very unhealthy relationship and might not have been able to do so if not for the entry of In-ji as an unexpected factor.
Then again, I am also not convinced about Seo-yeon wanting to extend her contract with her fake husband - I just didn't get the same inkling that she was as emotionally invested in the relationship as compared to him. It felt as if the story wanted to have a happy ending for her as well.
The set design and scenery featured in the drama also deserves special mention for the aesthetics and accentuating the atmosphere and vibe of the story. Jeong-won's huge house but with a cold and empty feel and the wilderness of the freezing lake where In-ji is in her kayak on her own provided a nice contrast with the warm and fuzzy feeling created by In-ji's ex-fiance's apartment filled with his belongings and their happy memories and the scenes where Jeong-won and In-ji enjoyed each other's company.
Since I think that the drama has probably tied up all the loose ends, I personally don't think that a sequel is needed. While I don't mind seeing Gong and Seo in another collaboration, it's probably unnecessary to come up with a sequel just to offer a clear-cut explanation of whether and how Jeong-won and In-ji end up together or not.
