 If you liked
InuYasha
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 ...then you might like
Takahashi Rumiko Gekijou Ningyo no Mori
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Protagonists on a journey trying to find something they desire to change who they are. In InuYasha's case, he wants to become a complete youkai. In Mermaid Forest, Yuta wants to become a normal human.
In the romance aspect, the protagonists are also really similar. Both had trouble falling in love for women who weren't immortal like them, and both series show a bit of how they dealt with it. Furthermore, they're by the same author, Rumiko Takahashi, and you can really feel her presence in the works.