S Chikkarangappa and Matthieu Pavon finished in a tie for second on 18 under after they both produced closing rounds of 67 at Four Seasons Golf Club Mauritius at Anahita.
Justin Harding fired a closing birdie to get to 17 under and finish alone in fourth, one shot ahead of Masahiro Kawamura and defending champion Dylan Frittelli, who notched seven birdies and no bogeys in his spotless 65.
Kitayama began the day alongside in-form South African Harding at the top of the leaderboard on 16 under and soon found himself one shot adrift after watching Harding confidently roll in his uphill birdie putt from around six feet at the second.
The 25 year old joined him on 17 under with a birdie at the next, holing his tricky 25-foot putt, with Harding unable to convert his long birdie effort.
After sending his approach at the long fourth to 15 feet, Kitayama rolled in his eagle putt to jump to 19 under.
Harding, who has won twice on both the Asian Tour and the Sunshine Tour in 2018, tapped in for a birdie at the same hole to stay within touching distance.
But Kitayama doubled his advantage after draining his ten-foot putt at the short fifth to get to 20 under par.
After missing his ten-foot par putt at the seventh to drop his first shot of the day, Kitayama steadied the ship with a gutsy par save at the short eighth after sending his tee-shot into a greenside bunker.
A run of pars was broken when Kitayama tapped in for a birdie at the long 13th, and he found himself three shots clear at the summit when Pavon dropped a shot at the 15th.
But a bogey at the 16th, coupled with birdies from Chikkarangappa and Pavon at the 17th, saw that advantage cut to just one shot.
Kitayama showed nerves of steel, though, sinking his tricky birdie putt on the 17th green to double his lead.
He then knocked in his par putt at the last to clinch his first wins on the European Tour, Asian Tour and Sunshine Tour.
Kitayama said: "I'm just so proud, really happy.
"It's an unbelievable moment for me, I’m just so happy I was able to pull it off.
"There were definitely some nerves around the first tee-shot. Going birdie-eagle-birdie helped to calm things down for the rest of the day.
"I was aware a little bit of what was going on, I kept one eye on the scoreboard.
"I just tried to stay calm and take it one shot at a time. It was important on 13, to get back with another birdie. I just tried to stay patient.
"This whole year has been, well, what a great year. I still have two more events but to win on one of the last events of the year is just great.
"It’s been really exciting, being able to travel all over the globe and I’m going to continue to travel more. I’m really looking forward to it."
Chikkarangappa reached the turn in 34 after picking up shots at the third and seventh.
He then took advantage of the long 13th before making further birdies at the 16th and 17th to post a bogey-free 67.
"It was a fantastic round today," he said.
"I’ve played to a solid finish today, which was much needed. I’m very happy with it."
A bogey at the short eighth threatened to stall his progress but he made another birdie at the 14th before carding a bogey on the 15th and a birdie at the 17th.
He said: "It was a fantastic week, I played really well and I enjoyed the week."