Claiming a Japanese dependent – household/country complications

Hi all, I'm asking this for a friend so ignore any tags for me. Friend is Japanese, friend's mum is Japanese but lives abroad. Friend currently lives with Japanese Grandmother in Japan (Grandmother is head of household). Friend's mum is not doing too well and is seeking health care in Japan, she will move to Japan shortly and live with friend and friend's Grandmother. Friend's Mum will be unemployed.

Friend will move to her own place shortly, before the end of the year. Friend will support Friend's Mum for relocation, hospital bills etc.

With these complications of the housing arrangement and country, is there any way for my friend to claim their mother as a dependent on their 確定申告? If there is, are there any stipulations/requirements that they must follow? And if successful, what is the deduction?

Thank you! I am only familiar with the tax law for dependents living out of the country so I am unable to help them in this case.

by ViralRiver