The American had countryman Justin Thomas, Mexico's Abraham Ancer and Australian Cameron Smith for company at nine under as the final Major Championship of the 2020 Race to Dubai moved towards being back on track at Augusta National Golf Club.
With almost three hours lost to inclement weather on Thursday, all of the players in the second wave will have to return to complete their second rounds on Saturday morning, but the leading quartet were in the clubhouse in Georgia.
American Patrick Cantlay and South Korean Sungjae Im were also in the clubhouse at eight under, with Spaniard Jon Rahm a shot off the lead with six holes to complete, and Japan's Hideki Matsuyama at the same mark having played 15.
Johnson - the 2016 U.S. Open champion - picked up birdies on the 12th, 15th, 16th and last to share the lead as he completed his first round and he was threatening to run away with it early in round two.
He parred the tenth but then played to ten feet out of the pine straw on the next, put his tee shot to 12 feet on the 12th and birdied the 13th after laying up to get to double figures and lead by three.
But a three putt on the next and a trip to the water on the 15th dropped him back, and he needed a closing birdie on the ninth to get back into the lead.
"I'm pretty pleased with the way I played today," he said. "I hit a lot of really good shots. Gave myself a lot of good looks, just can't really roll any putts in.
"I just need to play the par fives a little bit better over the weekend. I think that's the only thing that I need to really do any better is just figure out how to get some better looks on the par fives."
Two time Australian PGA Championship winner Smith made five birdies in nine holes as he finished his first round to get to five under but he was one shot worse off as he stood on the 15th tee in round two.
But he put his second at the par five to seven feet for an eagle, his tee shot to similar range on the next, and then holed a 25 footer on the 17th before making another gain on the last to pick up five shots in four holes.
Thomas - the 2017 US PGA Championship winner - had a roller coaster of a round, recovering from bogeys on the tenth and 13th with four birdies in a row from the 15th.
He had to play out sideways on the first and conceded a double bogey put made gains on the second, eighth and ninth to move back up the leaderboard.
European Tour member Ancer started his round with a bogey but dialled in his irons and made gains on the 12th, 14th and 16th.
He then took advantage of the par fives on the front nine and holed an 18 footer on the sixth in a 67.
"I kept telling myself that sometimes the best rounds start with a bogey, so I just kept telling myself that," he said. "Very patient - the golf course, you have to be extremely patient, and I've been able to do that these two rounds.
"I didn't really hit it my best off the tee, felt like I got away with some wayward shots that I normally don't hit. I missed a couple right but I've been able to scramble really well and made some putts for birdie which is what kept me in it. I played the par threes really good."
Cantlay fired a second round 66, with Im carding a 70, while Rahm was making a big move.
He took advantage of the par five second and eighth, holed a long putt on the fourth, hit an excellent approach at the ninth and made a 13 footer on the 12th before the light closed in.
Willett recovered from an opening double bogey with an eagle and six birdies despite having to play without a driver, while Fleetwood made one bogey as he also carded a 66, and Rose signed for a 70.