detailed spoilers:
He feels resentful that his gift was only an afterthought from preparing wedding gifts and feels like a fool for thinking he meant more to the ML.
So, a few days before the ML's official wedding day, he plans an elaborate scheme to escape and lay low in a remote hut to hide out for a few months before planning to reuniting with his father (who will retreat to a country-side residence due to his declining health) away from the main house where the ML will live with his new wife, since he can't bear to stand the humiliation of being a toy to someone he loves who 'does not love him back'. He spikes the meal of a servant ML brought to monitor MC with the help of his attendant and slips away without being caught. He runs away with his attendant, sells important belongings that could identify him, and disguises himself as a monk all in order to shake off trail of ML, who after discovering his disappearance, personally searches for MC himself with bounty hunters. After almost getting caught but narrowly escaping, he set up a house in the mountains close to a village.
ML appears out of the blue and captures his attendant who went to the mountains to collect mushrooms and threatens him to expose MC's whereabouts. MC was not in the house at the time bc he was worriedly searching for the attendant when he did not return before sunset, and came back in time to witness the scene of ML interrogating his attendant. He attempts to run into the mountains to evade ML, but ML ofc notices and chases after him. He gets caught and dragged back to the mountain house where he gets thoroughly punished (18+). ML is super mad and threatens to lock up MC if he dares to run away again and forces MC to promise that he will stay forever with him. After punishment, ML promises that he will never get with anyone except MC bc he realized that MC loved him when he found a box hidden in MC's room containing documents that exposed ML's family was guilty of treason and were executed, which MC could have used to have ML be executed, but MC purposely did not betray ML despite "hating" him. ML thinks MC ran away to get the ML to call off the wedding to chase MC. MC reacted with "???"
They return back to the house where both get scolded by the father, ML gets scolded for calling off the wedding to search for MC and ruining potential boost of family standing, while MC gets scolded for running away without notice and not taking studies seriously.
ML appeases father's fury by promising that he will tutor MC to pass exams to be scholar in 3 years time and father agrees. After father leaves to the country-side, ML promises to MC that he will love him in place of MC's dead mother and father's absence and swears to become MC's right hand man so MC can be the household lead. ML allegedly becomes more gentle-- except for when he's tutoring-- towards MC. The end. (They don't depict much happy relationship stuff afterwards)
(sorry it's so long, hi if you read till the end)

i regret reading the novel ... it was just like reading a horror story where mc never escapes and is doomed forever. They "love" each other but it certainly doesnt feel that way.