Nice catch! I didn't even make that connection! I'm excited to see its conclusion finally, if that is the case.
Also, re: Asahi selling Yotsuyu is weird "because he's so young." I don't think there's any likelihood whatsoever he did this as a child. I would definitely expect him to concoct this plan while in Garlemald proper receiving his education. I don't believe we're given any indication of how old that Echo flashback was--you figure it was 25 years ago Doma was annexed. You figure that gives a whole 24 year window (let's say ~10 minimum) that Asahi comes up with this. Do we ever know how long Yotsuyu was married? Eh? Do we even know she was sold to a Garlean? She just says "a vicious old drunk" and then when she's sold a second time to pay her ex-husband's debts does she become an Imperial spy.
We also know Gosetsu knows Yotsuyu's ex-husband he was sold to and it was a distinctly Doman name "Sashihai." He also refers to her as the "orphan of the Naeuri" which is ... curious? The Garlean says the Naeuri would receive compensation for Asahi's training. The mention of these names to her is precisely what leads Yotsuyu to step on his head in Isari.
Heh, in this very quest Yotsuyu compares her sins to Gosetsu's. Both survivors, both pledging loyalty to the Empire to further their own goals despite having no love for it. (Yotsuyu to get her revenge on Doma, Gosetsu to return to his master's side).
Given limited wikipediaing, in Japan, 96% of women take their husband's surname and it's a requirement for a couple to have the same last name to receive married status. (Of note, this is obviously the MODERN day, and not whatever medieval period Doma in XIV is based off of.) Which... makes me curious... Asahi's mother (married) is Naeuri, and her sister was also Naeuri (Gosetsu says Yotsuyu is an orphan of the Naueri) ... shouldn't this be impossible? Yotsuyu's family is definitely muddled. All languages refer to the Naeuri family being compensated for Asahi's prowess or something. Unless Yotsuyu's mother and Asahi's mother married into the same family.... I think there's something ridiculously hidden here, lol. Naeuri is definitely the "surname" / "house name" / "family name" but I'm having difficulties finding the dialogue I linked above in other languages currently.