Best Mobile App

Hi, Daniel-san, JR pass team!

Greetings I will be coming to Japan this coming January for 2 weeks and I after reading hundreds of blogs related to your train system I am still confused :) Is there an app that you can recommend that we can easily understand when trying to ride your train system? Thank you so much!

Also, we will arrive at Kansai International Airport and we'll be leaving at Narita airport after 2 weeks. We will only get 7-days JR pass and will active on first week - however how much will it cost from Tokyo Station to Narita airport one way when we leave?

Thank you again! Arigato gozaimasu! :)