nagihiko way i spell it im only saying this way because thats how its spelled in the anime subbes and manga

It could be either way, Nagehiko is how I spell it. In Japanese 'e' sounds like a short 'i' so I don't think there's is a correct way to spell it. Hope this helps!

I think its N-A-G-I-H-I-K-O

N-A-G-I-H-I-K-O F-U-J-I-S-A-K-I