Mory recorded the lowest round in a European Tour event to open up a one-shot lead over the field following his course-record seven-under par 65 on Thursday.
The Frenchman made light of consecutive bogeys on the back nine by going birdie-eagle on the 16th and 17th to open up an early advantage over Danish home hope Lucas Bjerregaard and South African Brandon Stone.
They were one shot clear of Italians, Filippo Celli and Francesco Laporta, China's Wenyi Ding, Finn Oliver Lindell and Germany's Freddy Schott.
But Buchanan, who is No.721 in the world rankings, enjoyed a fine start with his four-under 68 which featured five birdies and a bogey as he sat handily inside the top 10, three off the pace.
Buchanan, whose best effort this season was his tied-18th position at the Australian Open, enjoyed a strong finish with birdies at the 16th and 17th.
The 31-year-old Mory had missed 12 of his 16 cuts so far this season, but looked in blistering form.
"I struggled a bit at the start of the year," he admitted.
"I didn't think it was going to take me so much to adapt to this new tour and I didn't think it was going to be so different."
Starting on the 10th hole, Bjerregaard had the home fans behind him as he birdied the 12th, 13th and 16th to quickly make his move before eagling the 17th from six feet.
