Heading into the weekend in the Hero World Challenge, DeChambeau holds the lead after carding a brilliant eight-under 64 in the second round at Albany Golf Club in the Bahamas.
Morikawa, who won the DP World Tour Championship in Dubai less than a fortnight ago to become the first American to top the Race to Dubai, is once again proving his machine-like qualities here.
The two-time major champion carded an eagle and six birdies as he moved to 10-under, having shared the lead with DeChambeau before finishing with a bogey for the second day running.
“When I put myself in the fairway, I was converting, I was making the birdies when I needed to,” said Morikawa of his day’s work.
“Still felt like the driver's a little off, but, you know, get a little timing a little bit better tomorrow and the next day and we'll be just fine.”
The 24-year-old, who got engaged earlier in the week, smiled when it was pointed out that the fans could be set for a clash of styles over the final 36 holes.
“There hasn't been one style of golf that has won every tournament out here, right?” said Morikawa, who will topple Jon Rahm as world No 1 if he can land the title on Sunday.
“Look, Bryson's changing the game and he's doing what he thinks is going to help and I'm doing what I think is going to help.
“I think when it comes down to it, you know, who's going to put the ball in the hole with the least amount of strokes and we're all trying to figure that out.”
DeChambeau moved into pole position with an effort containing an eagle and 10 birdies, with his only blemish being a double-bogey 6 at the 16th after he found a bush.
Rory McIlroy, who shared the overnight lead, slipped four shots off the pace after having to settle for a 71.