Karin and Sesshomaru is one of my favorite oc x canon couples. The ultimate battle couple, the ultimate Prissy Bitch couple, the ultimate service top/pillow princess couple. Always Thinking about Them™

In the ‘yasha verse, the Kobayashi family is a youkai family on the Japanese side, and African American rootworkers on the Black side. It was Karin's grandmother (already fused to a spirit) who came to Japan, and fell in love with (kills yashahime with a sword) the lord of the eastern lands. A lot of Family Drama ensues when he married her and they have twins Sachi and Shio, and their aunt is the one who rules the Eastern Lands after killing her brother and reducing her sister-in-laws and niblings to servant status

Sachi married a human general (demon hunter, perhaps 🤔) and had a gaggle of children, and Shio married a demon woman and had a single son, Karin

Essentially Karin would meet Sesshomaru thru Inuyasha and Kagome, set around the same time the anime-which-shall-not-be-named takes place. At this point, they have their lil girl already. Karin approaches them to ask for their help in defeating the Lady of the East who is doing Shady Shit with half-demons (neglecting to mention she's his grand-aunt and he intends to take her place). At some point Sesshomaru gets involved and Love Happens

Idk if Karin takes his place as Lord and married Sesshomaru anyway (very on brand) or lets his aunt Sachi or one of his cousins take the spot (unlikely, he is a powerhungry lil shit) so he can marry Sessh without a conflict of interest 🤔

He is a very "I will have my cake and eat it too," kinda person so he will probably be like, "Why can't two provincial lords be gay and get married 🤷🏾‍♂️"

And ofc at the end they have one set of twins themselves (trans rights babey) and it's all good and nice