It is possible to maintain the patent by paying a doubled maintenance fee within six months after the due date.

The annuity fees for the 1st to 3rd years must be paid as a registration fee upon issuance (within 30 days from the forwarding date of the notice of allowance). The fourth year annuity must be paid during the third year or prior thereto from the date of registration. In Japan, no annuity fees are required for pending applications.

See “3. Annual fee / Registration fee” of the Schedule of fees on the following URL:
Schedule of fees | Japan Patent Office (jpo.go.jp)

It takes at least one week from the date of payment of the annuity until it is updated to the JPO register. If the payment is made by paper, it takes about one month from the date of payment of the annuity until it is updated to the JPO register.

In order to be updated in the J-Plat Pat (JPO website), it takes 1.5 – 2 months from the date of payment of the annuity.