In Kamisama Kiss, since the one Tomoe loved in the first place was Nanami disguised as Yukiji, he never actually loved the real Yukiji. But at the end of the anime, Mikage only told Tomoe that Nanami was a descendant of Yukiji, and I don’t think Nanami also told him that she was actually the one that Tomoe fell in love with 500 years ago.
So did Tomoe end up knowing that the Yukiji that he fell in love with back then was Nanami disguised as Yukiji?
Tomoe realized that the woman he fell in love in the past was never Yukiji, but really Nanami, who was actually the descendant of Yukiji and her child. The two then start a relationship to keep their promises of the past. It is explained in Kamisama Kiss: Kako-Hen that the “Yukiji” who Tomoe met was Nanami who was travelling back in time to save Tomoe. If Yukiji were to ever meet Tomoe, she’d try to kill him. Yukiji absolutely detests youkai, so there is no way that she’d ever love him as well.
Tomoe has been in love with Nanami this entire time, he just believed that she was Yukiji. Source: https://kamisamahajimemashita.fandom.com/wiki/Tomoe
