I'm searching for this AO3 Stucky fic I've read recently. It was A/B/O with non-typical Alpha/Beta/Omega dynamics based on some kind of fish gender-dynamics (it was even specified in the tags, but I can't remember which fish it was). There was this awesome complex world-building based on the concept of fish-like ability to biologically switch genders at will with the consequent differences like different family structures and lingo and courtship and grooming rituals and so on.
Bucky and Steve first meet in modern times while on SHIELD mission. They have the same backstory, but didn't know each other at forties. Steve is an A, Bucky switched to O after defecting from HYDRA with prejudice. Instant attraction, problems with communications since Steve doesn't know how to speak with other humans and Winter Soldier doesn't know how to human. Steve bakes Bucky some scones, draws him a cute card (art was included) and invites him to picnic date. Then takes Bucky home to give him a bath and braid his hair.
The whole fic is this amazing story about both of the boys being huge dorks and nesting. Please help me find it! I need it desperately!