The 28-year-old former Scarlets, Leicester and Gloucester playmaker is heading to Osaka to play for the Red Hurricanes.
But Williams says a move to the Far East doesn’t mean he has ruled out wearing the Three Feathers again.
“It’s everybody’s dream to play for Wales and three caps isn’t enough for me. I want to play for Wales again,” Williams told Scrum V Rugby’s podcast.
“It could be in a year’s time or even two, but there is no doubt I want to do it again. My initial contract in Japan is now down to 10 months and I will only be 29 when I come back.
“I might love it and stay there for longer – I’m open to anything.
“Playing in Japan became an option. I had been out for almost a year with an injury and everything just fell into place.
“This opportunity might never come around again and I didn’t want to look back when I am 50 and say I wish I’d taken the chance to go and play there.”
Williams has three Wales caps to his name.
He made his debut in a win over Tonga – a game played at Auckland’s Eden Park – in June 2017.
Williams then started at centre against Australia and New Zealand in that year’s autumn internationals but hasn’t played since.
He was in Wales’ squad for the 2020 Six Nations and was on the bench for the visit to Ireland only to suffer an injury in the warm-up and have to pull out.
“I spoke to Wayne a few times and he told me it would be better for me to play in Wales if I was going to play for him,” added Williams.
“I let him know what I was thinking and I also let him know when I had made up my mind to go to Japan. He was really nice about it and said we would stay in touch.
“There are no guarantees in sport and coming back to Wales wouldn’t have guaranteed me getting another cap. I would have had to stay fit, play well, and convince the coaches to pick me.
“I prefer to play at outside-half because I like kicking and calling the shots. Playing at inside centre is probably harder physically.
“You are hitting more rucks, making more tackles, and chasing more kicks. It’s more demanding mentally playing at No 10.”
