In general, it is very difficult for foreigners with mid-long term status of residence (i.e. visa) to bring their aged parents to Japan and to take care of them for a year or so.
A foreigner wishing to stay in Japan must obtain a suitable status of residence for his/her activity. Yet, there is no status of residence for aged parents to be looked after by their son/daughter (including in-law) except for parents of foreigners with status of residence “Highly-Skilled Professional”.
However, it may be permitted if there is a considerable reason. In this case, an applicant (aged parent of foreigner with mid-long term status of residence) may be allowed to change to the status of residence “designated activities” after arriving in Japan as a temporary visitor.
According to the Immigration Services Agency official, since there is no specific status of residence for aged parents to be taken care of by his/her son/daughter staying in Japan, there is no specific eligibility standard. Hence, it is impossible for them to answer any specific questions such as requirements, conditions, etc. In addition, they will assess each application based on applicant’s special circumstances.
The following information is based on my knowledge and for your reference only.
1. Where to inquire and to submit an application?
Depending on your status of residence. For instance, if you have a status of residence “Permanent Resident” and currently lived in Tokyo, “Permanent Residence Inspection Department” at the Tokyo Regional Immigration Bureau is the right place for you to inquire and to submit an application for your aged parent.
2. What documents to prepare?
(1) Documents explaining why you need to bring your aged parent to Japan as well as supportive evidences for them.
Please note that simply your parent is XX years old is not enough reason. You need to explain a special circumstance such as your parent has a disability and/or needs nursing care, there is no family member in the country where your parent lives, hence no care-giver is available for your parent other than you take care of your parent in Japan.
(2) Documents explaining that you can support your aged parent to stay in Japan financially as well as supportive evidences for them.
Even your annual income is X million yen, if you are supporting a big family, X million yen may be considered as not enough to support extra person (i.e. your aged parent). Hence, your disposable income is more important. In addition, your bank deposit or other assets can be alternate supportive evidences of your wealth.