Fangraphs on Kikuchi:
He possesses three pitches with fantastic whiff rates, but his biggest issue is the amount of hard contact he allows when batters do connect with his pitches. His inconsistent mechanics are likely the root cause of his struggles. Beyond the potential tipping problem his two release points creates, his command is likely compromised without a repeatable delivery. He’s able to control his pitches in the zone, but his inability to hit his spots regularly led to far too many hittable pitches. In order to maximize his weapons, he should fade the usage of his cutter in favor of more sliders thrown on the edge or below the strike zone. He’ll likely continue to allow a bit too much hard contact off his fastball, but its ability to generate a high number of swings and misses means it’s a crucial part of his repertoire. But all these potential adjustments won’t mean much if he can’t figure out his mechanics first.
Basically: throw fewer cutters. Rely more on his slider, and focus on throwing them on the edges or out of the zone as an out pitch. Clean up his mechanics enough to remove any pitch-tipping. Keep dudes off base well enough that you can live the hard contact.
If all of that looks familiar, it's because it's very similar to what we did with Ray last year. Ray largely focused on his FB/SL and used his CB much less, and caught a lot of plate with the FB while fading the slider. Even though he gave up a lot of hard contact, having to respect the slider made his (often straight, meaty) FB play up. That Kikuchi has a second good out pitch doesn't hurt in reconstructing his repertoire, either.