Scouting Asia has become a full-time operation for a number of MLB teams. Here are a few that I expect to see watching Japan this season.
Note that I haven't included the most obvious teams here; by now it isn't a surprise if the Red Sox, Dodgers or Mets are in the mix for a Japanese player. Nor is it meant to be an exhaustive list; there's always room for surprises.
Texas Rangers: Pacific Rim scout Jim Colborn's name shows up in the Japanese media fairly frequently. Colborn coached in Japan in the early 90's and has Kazuo Fukumori and Yukinaga Maeda. He was last seen scouting a couple of pitchers from Hosei University. Texas also had the top dollar offer for Junichi Tazawa but were rebuffed for Boston.
Toronto Blue Jays: The Jays set up a Pacific Rim department last offseason, headed up by former Nippon Ham Fighter Rob Ducey. They also signed lefthanders Ken Takahashi and Shigeki Noguchi to minor league deals over the offseason, though Noguchi failed his physical. The linked report indicates they'll be looking for more central pieces as the department ramps up.
San Francisco Giants: Not much to go on here, but Asia scout John Cox's name has shown up in the media a couple of times. I can't think of a notable Japanese/NPB signing the Giants have made (unless we count Masashi Murakami) so we'll see if they make one this year.
New York Yankees: Gene Michael made a trip to Japan last year, reportedly to watch Yu Darvish. I expect that they'll continue to monitor top guys like Darvish and Norichika Aoki as longer-term prospects, but not be hunting for bargains or middling players.
Atlanta Braves: Signed Kenshin Kawakami and Yoshinori Yamarin last season, and also made a strong bid for Tazawa. Atlanta has also signed minor league-level amateurs such as Ryohei Shimabukuro and Kazuhiro Takeoka in the past.
I'll have a list of guys they might be competing for within a week or so.