SPOILERS AHEAD !
My biggest problem with the story is what i'll talk about below, if you still want to enjoy ~65 chapters of a competent and funny story with pretty boys and pretty art (and although this is NOT an in-depth plot summary anyway) I reccommend skipping this review and checking it out yourself first, unless practically story-ruining endings are a dealbreaker for you.
Being a work of Honey Trap, To Deny The Route / How To Refuse The Route was always going to be at least a little good. Honey Trap, who is best known for Guild Member Next Door / Virtual Strangers, is very talented at writing both a likable MC and LI, creating a very fluffy and compelling relationship between them, comedy, conflict, and straying away from typical manhwa tropes. I'm especially a big fan of the way they poke fun at overused tropes or series that romanticize things like noncon or incest. Not only does HTRR directly address those tropes, but it also twists the royal reincarnation story in an interesting way.
Our nameless protagonist suffers a classic truck accident that isekais him into the body of the five-year-old son of a count and a victim of a drowning incident that left him in a coma for a year prior to when he wakes up. The usual status window that pops into existence when he awakes to his parents and three brothers tells him that he's become the protagonist of a dating game, Jerry Route (Get it?). He's able to see tips and tricks to events that are about to happen in his life, quests forced upon him by the system, second most importantly, his stamina levels (that begin so weak that he passes out anytime his stress surpasses a certain number), and most importantly, the likeability of the dating options around him.
As far as he knows, there are six routes available, some of which include his brothers, which he is openly disgusted by and refuses at any possible opportunity. A real rarity in the world of BL manhwa. While he's grappling with the fact that he now lives in a world that feels completely fabricated and out of his control due to being centered around him and the system, he is whisked off to the royal palace, known for some of it's members having infamous bright red eyes, which are signs of powerful and feared rulers. Three of these members are Karyan Deferious (Get it?), the crown prince, Sears Neur, the court mage, and Ilya Deferious, the disgraced son of the family.
Karyan, though rude to him at first, takes a liking to Jerry after he treats Karyan not as a noble, but as a regular kid, even hinting at a bit of a masochistic personality and becoming possible love interest as his "likeability points" increase after being kicked and berated.
Sears, a talented mentor who has cast himself out of the royal family to focus on magic, finds it fun to mess with Jerry as the mana surrounding him gives away his emotions, and keeps placing truth spells on him as a form of magic training, the route of the game that Jerry happens to be most interested in.
And Ilya, despite the story trying to get you to believe for even a second that he's not, is our main love interest. He's a somewhat gloomy and quiet fluffy-haired lonely boy who runs around and hides in the kingdom gardens, becoming quickly attached to Jerry due to being shunned by everyone else in the palace except him and Sears. Ilya's skill with magic is far past his age, so he even joins Sears in lessons to spend time with and help Jerry, replenishing his mana whenever his stamina dips dangerously low.
The story has a couple short timeskips here and there, the biggest one being from age six to eleven when the system forces what is essentially magic PTSD onto Jerry after he, Karyan, Ilya and Sears take a boat ride that triggers Jerry's original body's memory of the drowning incident it suffered from, rendering him unable to meet with the three of them or go near water without instantly fainting.
The system is honestly nothing short of cosmic horror when it comes to forcing things onto Jerry, being as painful as it is helpful.
This is the beginning of a big development for Ilya as well, as during the timeskip he trains his magic to an almost uncontrollable degree under the guise of wanting to protect Jerry. After the five years and an additional skipped year are up, Jerry is ready to enter the academy, which is where he'll grow closer to Ilya and Karyan, meet new roommates Siren Gracier and Henry Gardner (a pair leaning towards becoming a side couple of their own!), learn more about the system itself via a "guidebook" that tells him a bit more about his fate depending on the route he chooses, meet a mysterious fortune teller who somehow has insider knowledge on the "game" Jerry is trapped in, and of course, improve his magic overall, which is what the story begins to most heavily focus on aside from Ilya's affection.
The magic in the world is your usual take on mana and spells, but the way Jerry is able to use his sliders to set his stamina back, control his sensation of pain, and how he keeps pushing himself alongside his new constant pain seemingly stemming from his original-world truck accident sets up for disaster, becoming something unique that both contributes to the mystery of the worldbuilding and works as an excuse to spend more time with Ilya, who is now very obviously both attracted to and purely in love with Jerry, who is only distraught as he believes anyone could only ever love him as a result of the system and status window. We're greeted with another timeskip, and now Jerry is sixteen. As our knowledge of what the magic can do and what happens behind the scenes of the royal family grows, the story starts introducing Ilya's backstory, rivals, new mysteries, new side plots, new steps towards character development for Karyan, Sears and the others, reveals Ilya could always sense the status window's mana and begins to be able to see it, and even hints that we could get backstory on how both fake and real Jerrys ended up at reincarnation, Jerry starts to figure out his feelings that he might also be falling for Ilya, beginning to learn how to free himself from the dark future spelled out for him in the game, and we...
Get another timeskip...
And then, without closure on how Karyan feels about Jerry and Ilya, how the lives of Jerry's other friends end up, what happens to Sears, the fortune teller, Jerry's brothers, people who have been trying to use magic to curse Jerry, and even the mysteries of the system itself... the series ends with a single rushed chapter showing Ilya deciding to leave the family and take Jerry's last name in marriage so he can work as a powerful mage with Ilya by his side, them being practically the only ones with what you could call a complete character arc.
Whether Honey Trap was forced to end the series here due to cancellation or other obligations, put under restrictions of the publisher, or simply couldn't think of a way to wrap up the dozen unfinished character arcs and unsolved mysteries, the story suffers greatly for it, and takes away points from what would have otherwise been a heartwarming yet intruiging story about changing your fate and learning to trust and confide in the people around you while accepting their support and deciding for yourself what you want to do. So, what started as such an enjoyable story ended up an unfinished and unsatisfying regular reincarnation BL ending with a shallow conclusion and no side stories to further explain, explore or redeem anything else.
Ultimately, HTRR had such great potential, but in the greatest form of irony, finished with the same type of ending Jerry himself had been trying to avoid the entrire time.