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So last month I talked about guessing Sano's real name as Susanoo no Mikoto, glad that was right. I can finally sleep at night. jk. So what's left is to uncover my other theory that Yuuta is from the Kurahashi clan a branch of Tsuchimikado clan which are descendants of Abe no Seimei.
Ebisu and Sano don't share the same last name I think it was because Mikoto is really not Sano's last name. Gods dont have last names. Probably just took Mikoto and make it as his last name. Also for Ebisu's last name Isaburo, lore says when Ebisu was abandoned/casted away for being something like "defective" (no bones or broken bones I think) a fisherman picked him up and adopted him so I guess that's why his last name was different. I would also guess that Ebisu is also the name that was given to him. I mean this is just another guess.