Well, if he goes by train to Nikko from NRT then I believe then the best way is to take Keisei Sky access to the Tobu line or whatever they call it. So that's not JR.

In any case, getting a JR pass does not make sense as pointed out here by other people.

I don't think you would get much out of Nikko in one day by public transport since it's a large area. I haven't been there yet, but guess that I should go one day. Especially now that the radiation is a bit lower. It's still 4X the radiation level of Tokyo, I believe. I have Tochigi and Ibaraki on my food blacklist, so definitely not going there for the local cuisine.