The 24-year-old midfielder plays for Jubilo Iwata in his homeland and Hoops boss Neil Lennon has previously spoken of his admiration for the player who has played twice for the Japanese national side this year.
The official Celtic website confirmed the player was training with the Scottish champions at Lennoxtown.
Lennon told the Daily Record earlier in the month: "We're looking to bring him over to take a look at him.
"John Park (head scout) has watched him a couple of times and we've seen some footage.
"However, it's always good to see him up against the rest of the players and how he copes with it.
"He can play left side or off the striker. He looks okay but we'll not have a real idea until we've seen him over here.
"I don't think there would be any money involved - he's a free."
Meanwhile, skipper Scott Brown believes Celtic can remain unbeaten in the
league for the rest of the season.
Following the 6-1 Champions league defeat by Barcelona in the Nou Camp last week which ended their European aspirations for the season, the Hoops responded with a 1-0 win over Hibernian at Parkhead on Saturday which extended their unbeaten run in the Scottish Premiership this season to 15 games.
Asked if Celtic could remain undefeated through the entire campaign, the Fifer did not rule it out.
"We are a tight group and we are strong, and I think if we put our minds to it we can definitely do it," he told the official Celtic website.
Celtic will have to contend with a heavy festive fixture list which sees them host Hearts on Saturday, before taking on St Johnstone, Inverness and Partick Thistle in the space of six days.
However, the Scotland midfielder said: "It was a hard game in Barcelona and they have done that to a lot of teams - they have done that to Real Madrid as well - but we are back in our normal league position and going about the job the way we should be.
"A lot of teams have been spending 50-60 million pounds to get to the last-16 and our budget isn't as big as that. We managed to do it last year (get to last last 16) and it shows what a good team we have here.
"We have a run of games coming up, especially over the festive period which will be hard.
"The gaffer will make a few subs here and there, change it up and freshen faces, but the lads enjoy playing week in, week out and two or three games a week."
Brown would welcome any fresh additions to the squad when the transfer window opens.
"I don't know who we will bring in," he said. "We will need to leave that up to the manager, staff and board, but whoever comes in will be more than welcome."