The wife-to-be subconsciously knew she wasn't going to survive her wedding to her childhood love if she wore white. So she was resistant until she realized her murder was inevitable and gave in, becoming her husband's (first?) human victim.
Because love.
A childhood love who tortured and killed only white animals. White being one of his "tics", like how some killer's victims MUST female, brunette with blue eyes, 5'5 and 100 lbs.











Fits into Western "dark romance" genre very neatly.
Seme is obsessive, possessive and territorial. Also, VERY loyal.
Neither of them cheat on each other. No infidelity either.
Although it wouldn't be "cheating" if uke slept or pursued someone else until around ch 60. That's when uke catches unwanted feelings for his rapist. Before then it would be reasonable and even justified if he fell for or go to someone else for sex/love.