Nikko is a historical city 2 hours north of Tokyo in the Tochigi Prefecture.
Getting there is relatively easy although there is a small thing to know when taking the train in Kita-Senju. It appears that the express train needs a reserved seat ticket that you can buy, on top of your nomal train ride, at the gate to the platform
that platform is actually a bit like a Harry Potter special one! you need to go to the indicated platform in the station BUT once there, you need to walk all the way to the end and go through a special passage to a hidden platform for that train
you will then get a very vintage train all in brown velvet, so cute, kawaii desu ne
Enjoy the ride!
You may purchase a combined ticket that will include the return ticket and access to the bus in Nikko as well as the monuments. I did not as Nikko is a very walkable city.