The innovative event was making its European Tour debut, with the 144-man field playing two days of 18-hole stroke play and the top 64 then advancing to a nine-hole stroke play knockout, with the winner being crowned on Sunday after a total of 90 holes.
Detry gave his hopes of making the weekend a huge boost with a 67 that moved him to the top of the leaderboard on four under along with English pair Matthew Baldwin and Ryan Evans, Spaniard Jorge Campillo, Chilean Nico Geyger, Malaysian Gavin Green and Dane Jeff Winther.
Another local favourite in Nicolas Colsaerts was a shot off the lead alongside English duo James Heath and Sam Horsfield, Australian Nick Cullen, Frenchman Benjamin Hebert and Zimbabwean Scott Vincent.
The seven-way tie for the lead is the joint-third largest leading group after 18 holes in European Tour history but none of the players at four under have a victory on Tour, with Colsaerts the only winner in the top 13.
Huge crowds turned out in Antwerp as the European Tour once again broke new ground, and Detry could not hide his delight after a glorious day on the compositie course.
“What can I say? The first round here in Belgium in front of record crowds, shooting four under and finishing with three birdies like that, it doesn’t get any better,” he said.
“The course was perfect. Greens were firm and fast, which was good. It got a little windy out there as well so we’ll have to be careful on a few holes. I played some very good golf and I’m excited for the rest of the week.
“It’s just awesome to see some familiar faces, friends from home, everybody out here supporting. It’s just great for golf and great for golf in Belgium and great for me.”
Green was the first man to set the target at four under as the 2017 Asian Tour Order of Merit winner produced a birdie-birdie finish to go with gains on the eighth and 12th.
Geyger then joined him as he came home in spectacular style. After a bogey on the fourth and a birdie on the seventh saw him turn in 36, the 31 year old picked up shots on the tenth, 11th, 15th and last to surge up the leaderboard.
Baldwin was in the first group out in the afternoon and he soon joined the lead, making birdies on the tenth, 11th, 15th and 16th to turn in 31. An excellent approach to the fourth made him the first man to five under but he dropped back into the pack after failing to get up and down from over the back of the ninth green.
Detry birdied the first and put an approach to six feet on the tenth but gave a shot back on the 13th before a brilliant finish. He drove the 16th green and got down in two putts, put a stunning approach to four feet on the next and a ten-foot putt on the last had him at four under.
Playing partner Campillo turned in 33 with gains on the first, sixth and seventh and, after a bogey on the tenth, added further birdies on the 13th and 16th.
Evans shared the lead after the opening round of last week’s Rocco Forte Sicilian Open and he was at it again, turning in 31 with birdies on the tenth, 11th, 16th and 18th. A bogey was to follow on the first but he moved back to four under with a gain on the eighth.
Winther made a fast start with birdies on the second, fourth and fifth, and bounced back from a bogey on the seventh with further gains on the ninth and tenth.
Colsaerts had delighted the large local gallery following him with birdies on the 16th and 18th, and he made another on the eighth before an excellent par save on his final hole after going right off the tee.
Horsfield was bogey-free in his 68, with countryman Heath finishing with his only bogey of the day to drop out of the lead.
Hebert recovered from an opening bogey with birdies on the 14th, 16th, third and fifth, while Cullen and Vincent both made two bogeys in their rounds.
Tournament host Thomas Pieters will need a solid Friday if he is to make the weekend after an opening 73 left him in a tie for 84th, one shot off the cut.
India’s S.S.P. Chawrasia got off to a terrible start. He made four bogeys and two doubles, ending the day with a 76.