You can file a divisional application during the period as below:

– Period from filing of the original application to start of the examination by the examiner (i.e. the period in which a voluntary amendment can be filed);

– Period from issuance of a Notice of Reasons for Rejection to the time limit for Responding to the Notice of Reasons for Rejection;

– Within thirty days from the delivery date of the certified copy of a decision of grant a patent (except for a case where the patent is granted after a request for appeal against a decision of refusal is filed);

– Within four months from the delivery date of a certified copy of the first Notice of Decision of Refusal (*when the applicant is a resident outside Japan)

In Japan, a divisional application can be filed during the period and or at the timing as above for the parent application as long as the parent application is pending in the JPO.  You can file, for example, a second-generation divisional application based on the first-generation divisional application, and a third-generation divisional application based on the second-generation divisional application.