How Japan National Healtcare System Works?

Hi!

I'm planning to apply for the MEXT scholarship, and I have doubts about how the National Healthcare System works.

1. How can you enroll in it? Theres plans and you have yo pay or what?
2. Is there a website where I can check what kinds of meds they cover? I'm a kidney transplant recipient,t and I need to see if they cover my meds.

Those two questions are my main concerns.

Thank you all for your help!