The problem is that much of Takeda's success seems to be batted ball related, as he has a 4.44 kwERA over that time with a 14.7 % strikeout rate. He has given up homers to just 1 percent of the batters he has faced, and walked just 6.6 % of hitters, meaning that while he doesn't strike anyone out, he doesn't give up homers or walk people either. This means that he gives up a lot of batted balls, and it appears that he is getting an unusual number of them turned into outs. This year he has a 59 ERA -, but is striking out less than 13 percent of batters faced, over four percent worse than league average (not adjusted for starters or relievers). So while it is hard to argue with his run prevention abilities, it is difficult to tell how much of it is him just taking advantage of the often run starved NPB environment. The first and most natural reaction seems to be to write off Takeda as a MLB prospect because he is not missing bats at a lower level so it is unlikely that he will miss bats at a higher level. However, I'll dig a little bit deeper than that.
From a scouting perspective, the first thing that stands out about Takeda is his height and size in general. He is listed at 5-7 and 161 pounds, laughably small for any professional athlete, especially for a successful pitcher.
Takeda compounds the lack of height with a really low release point thanks to the way he spreads out, as this photo from the Fighters' official site shows:
Takeda is known to throw a fastball that gets up to 91 MPH on his best days and averages about 87. When watching him, I saw a lot of 138-139 km/h (about 86 MPH):
The whiff on the fork is especially amusing, and it appears to be his best pitch. I do like his curve because it isn't too loopy and slow, though I think the slider is too soft and doesn't differentiate between the curve as much as you would like. For his fastball velocity, he seems to use it well, going arm side with the 2seam, and glove side with the 4seamer. Even at the NPB level, his fastball is more successful than the velocity would let on.
Because of the lack of fastball velocity and strikeouts, I don't think Takeda is a real MLB prospect, and I think his game wouldn't translate very well, though funnier things have happened, and it is really hard to quantify how the unique delivery and deception would play in a different league.