From best I can tell, there have been just 5 NPB hitters come to the MLB since the Pitch F/X era began, two of them have been really unsuccessful hitting shortstops, two had good starts but faded, and one is enjoying success in the Majors right now. We will start with him:
Norichika Aoki has been a nice player in the Majors so far, with a 3.7 WARP in 184 games and a 110 OPS +. However, the Brewers' submitted a bid of just 2.5 million for him, and knew so little about him that they made him go through a series of tryouts before signing him.
Here is how he was pitched in the first half of 2012:
Inside is where he has had the most success, showing that teams were right to stay away from the low and in zone. However, he is better on high balls than low balls. Here is where he has been pitched in his entire MLB career:
Teams have somewhat corrected now, throwing pretty much anywhere in the zone except the low and in zone.
Here is his 2007 Frequency, the first year he was in the big leagues.
Teams threw the ball very high and a lot of them away to Iwamura.
Here is his Career TAV map:
In his Career frequency map, we see that pitchers adjusted somewhat, but he still got a ton of pitches thrown up:
Kosuke Fukudome is usually considered a disappointment in Chicago, but he was a productive hitter in the big leagues until he was traded to Cleveland in 2011. He has since went back to Japan, where he is hitting .170/.262/.295 in 30 games.
Here is his 2008 Frequency map:
Here is his Career TAV map, which supports the conjecture somewhat, but also showed that he had a hole in his swing low and in:
Looking at his career frequency map, it seems that pitchers started throwing it low and in a little more, and while still keeping it away, got a little less absurd in doing so:
Munenori Kawasaki was not a very good hitter in Japan, so it is no surprise he hasn't been a good hitter in the Majors either.
Here is his First Half of 2012:
His career TAV map shows that up and away has turned out to be his best zone:
But since it isn't a big sample size, the career frequency hasn't quite corrected yet:
First half of 2011 (for convenience, since he was a switch hitter, I looked at just him versus right-handed pitchers, where there would be a bigger sample size than vice versa)
When looking at his career TAV, we see just how bad of a hitter Nishioka was in the Majors for whatever reason. Maybe it was the leg injury, maybe the pressure, or perhaps he just wasn't as good as the aesthetics of his swing or his NPB numbers suggested.
Another small sample size, so the map doesn't adjust a lot for his career frequency, though he strangely started seeing more balls low and in.
It seems that other than perhaps Nishioka, whom the Twins obviously whiffed on for whatever reason in the evaluation process, and Fukudome teams really didn't have much of a clue of how to pitch to the Japanese imports. Kensuke Tanaka and Hiroyuki Nakajima were both signed in the off-season by MLB teams, and they both haven't played in the Majors yet (obviously Nakajima was injured). It would seem with this evidence that MLB teams are/have been in recent years really poor at evaluating NPB hitters, whether it is which ones are good and worth signing and placing on MLB teams, or how to pitch to these hitters when they are on other teams. This will be interesting to keep an eye on if Takashi Toritani and Yoshio Itoi decide to come to the Majors after the 2013 season.