going to college in tokyo with a chronic illness

so i applied to international christian university in tokyo and if i get in, i’m likely to go there, it’s actually one of the only schools my parents can afford. i have a friend that goes there and she said that everyone has to be under the japan health insurance, but i was wondering if anyone knew how it works for people with preexisting conditions? i have lupus, rheumatoid arthritis, and raynaud’s disease. also does anyone know how it’d work to have my doctors appointments over there and get my meds sent? i know one of my meds is a controlled substance, but the super mandatory ones look like they’re approved in japan. and i’m proficient at japanese but not enough to have a medical conversation.