As of June 9, 2018, the six-month grace period for inventions/designs that have lost novelty will be extended to one year (Japan Patent Act Article 30, Japan Design Act Article 4, Exceptions to Lack of Novelty).
The JPO announced that the grace period for inventions/designs that have lost novelty due to an act either by or against the will of the person having the right to obtain the patent with respect to patent applications, utility model applications, and design applications will be extended from six months to one year. This amendment applies to applications that are filed on or after June 9, 2018.
However, this amendment does not apply to inventions/designs that were disclosed on or before December 8, 2017. Inventions/designs disclosed on or before December 8, 2017 has a six-month grace period.