The MC is not "Felmenia Stingray", its the generic black haired japanese highschooler. She's just the first member of his harem.

The real story is about how the MC is an OP mage who can cast spells without chanting and absolutely shits all over all the native world's mages, who for some reason have never been able to figure out how to use magic without chanting.

Then he goes on a journey and gets a harem. Sounds familiar? Yup, its the usual author self insert fantasy where he has OP powers and a harem