student visa and 80% attendance requirement

hi there, not sure if this is the right subreddit to post this on but here goes.

my boyfriend is currently studying abroad in japan, he has a student visa and is only there for 6 months (he comes home in february, finishes his course end of january).

while out in japan he developed epilepsy, he’s now having seizures like once a week and is super worried about his attendance. he’s seeing a neurologist and is on medication, his uni is well aware too.

so my question is – what happens if his attendance goes below 80%?

i know that he will be unable to extend his visa if this happens, but will he be deported? how long does will it affect his visa applications? is there some sort of clause that allows for lower attendance due to medical issues sustained while in the country?

for reference he is in Kyoto and from the UK. not sure if that’s relevant.

literally any guidance or pointing in the right direction of guidance would be a great help, as i cant find anything substantial online.

thanks in advance ♡