ML is an Alpha who's been "in love" with his childhood friend/neighbour basically all their lives. I used scare quotes because it would be more accurate to call his feelings a level of fanatical obsession that I consider not to be the sign of a sane, healthy mind.

MC is a Beta who struggles to form emotional connections - again beyond the range of what's considered normal, though I wouldn't go so far as to call it unhealthy; more your typical "low EQ" that lots of novel leads suffer from to keep the misunderstandings flowing.

They're joined in a marriage of convenience (from MC's perspective) according to state regulations. Despite the fact that he is a lifelong friend, closer to her than anyone but her nearest relatives, MC simply cannot trust that ML won't betray their marriage, since she believes all Alpha will eventually seek an Omega partner. Most of the novel is him trying to prove himself trustworthy, and win her affection.

... Seems to be written to appeal to the fantasy: 'having a studly Alpha Male be your s*ave/dog/doormat'. Literally, ML abases himself in front of MC to be stepped on, is continuously weeping and pleading with her not to abandon him, cosplays in servant's uniform/canine accessories, offers himself up in a chastity belt, handcuffs, and IDK what other paraphernalia since none of this is my kink and there was nothing else that interested me enough to keep MTLing. All the bits I did read remained within the realm of "suggestive" rather than "explicit".

ML's whining, clinginess, and outright stalking annoyed me; however MC ultimately annoyed me more since, no matter how rational a basis her fears may have, someone so determined to remain indifferent shouldn't get to indulge their jealousy and paranoia so much! Whether he ever asserted himself, or she relaxed her vigilance against him, I can't say since I didn't persevere to the end.