The Omega Takes a Husband
Omegaverse where our main (omega) charcater, being the sole heir to his yakuza family/group, needs to marry an alpha, because the yakuza world is old-fashioned and it is a custom that groups be lead by an alpha, while maintaining the hereditary nature of the boss' sucession. A lot of usual alpha scumbags, some attempted thingies going on. However, our omega is more than capable of taking care of himself most of the time. I was surprised by how strong-willed and considerative of his future he was, instead of being merely the hot-headed, overconfident alpha-hating omega type of character I thought he was going to be. The story isn't very elaborate or complex, it ends up being mostly centred on the 2 main characters without that much external plot. It's pretty okay, and I feel like the characters were a bit more well-developed than in most one-volume BLs like this.
Yonin no Nibiiro