NJPW is holding a post-Wrestle Kingdom 13 Press Conference today and it was announced KUSHIDA will be leaving the company at the end of the month.

NJPW Announcer Chris Charlton translated some of KUSHIDA's comments about "heading overseas."

KUSHIDA: As Sugabayashi said, I will leave NJPW on January 31. This was an extremely tough condition made with Meij, Sugabayashi and Kidani. It was a very big decision in my life and I'm thankful they understood. I will head overseas and to see the world of pro wrestling.
chris charlton (@reasonjp) January 7, 2019

KUSHIDA: I have been here in NJPW for 8 years. I was surprised at the scale of the business when I first came in and proud of being able to work here. The warm reception and words from the fans made me who I am and I am so grateful to them.
chris charlton (@reasonjp) January 7, 2019

KUSHIDA: I am contracted with this company until the end of January so I won't be talking much about beyond then. But it has been my dream for a long time to travel the world with professional wrestling. And that's what I will be doing.
chris charlton (@reasonjp) January 7, 2019

KUSHIDA: I increasingly took on the role lately of working with younger talent, and while not teaching, learning together. Along with that, going back and forth between ROH and New Japan I realised I am now 36 and have much less in front of me career wise than behind.
chris charlton (@reasonjp) January 7, 2019

As noted, WWE had reportedly shown interest in the former IWGP Jr. Heavyweight Champion, potentially bringing him into NXT.

During his time with NJPW, KUSHIDA was a six-time IWGP Jr. Heavyweight Champion, two-time IWGP Jr. Heavyweight Tag Team Champion, and two-time winner of Best of the Super Juniors.