Asaji was the only player of the 118 competitors to sign for a bogey-free round on the 7,068-yard (6,463-metre) West Course at Kasumigaseki Country Club, which lies one hour north west of Japan's capital, Tokyo.
The 17-year-old opened and closed his first round with birdies, making further progress in between with additional birdies on the ninth and fourteenth holes.
"I played perfectly today with no bogeys, and I only missed the green on one hole," he explained. "I think I play well at Kasumigaseki, so hopefully I can do better than last year, when I finished 41st, because I really want to play in the Masters in the future."
Australia's Jake Higginbottom has opened with a 3-under-par, 68, to be one stroke off the lead at the Asian Amateur Championship in Japan.
Higginbottom, winner of the 2010 NSW Amateur Championship, fired consecutive nines of 34 that included four birdies and a bogey to place the Australian within striking distance of the lead.
Jordan Sherratt, who secured a 3rd place finish at this event last year, fired an opening round of 1-under-par 70, along with Kieran Pratt to be currently in a tie for 11th and the next best of the Australians.
New Zealand's Ben Campbell and Aussie Tarquin MacManus opened with an even par 71 to be in a tie for 17th, to be only four strokes from the leader. Luke Bleumink had a 77 for his opening round and will need to make a move to have any chance to contend at this tournament.
Matt Jager's woes continue with the 2010 Australian and New Zealand Amateur Champion carding an 80 to be well down the leaderboard and effectively out of the tournament.
This was not the start Jager was after as he goes in search of the form that had him at one stage ranked number 4 in the world. The last few months have been a struggle for Jager and he's in need to produce something this week to give him any confidence moving into the World Amateur Championships in Argentina later in the month where Jager is part of a four-man Australian team that includes Sherratt, Pratt and US based Brian MacPherson.
Originally from the Newcastle region, Higginbottom plays out of The Australian Golf Club in Sydney and has made his mark already in main amateur events since progressing from the junior ranks at the beginning of this year.
Higginbottom, 16, powered to his biggest amateur career title so far when he accounted for England's, Tommy Fleetwod, 3&2, to win the NSW Amateur Championship back in February. As a 15-year-old he qualified for the NSW Open and in 2006, won his age group in all 25 Jack Newton Junior tournaments he played.
Want video tips delivered straight to your inbox? Subscribe to iseekgolf.com newsletters.