According to the Japan Times, in 2012, the late Kunio Yonenaga, then a retired pro, was beaten by Bonkuras, written by a programmer at Fujitsu Laboratories Ltd.
An active professional player has for the first time lost to the computer for the first time on Saturday.
The game was the second in a team contest that pits Sato and four other pros against five programmes that won the top places at last year's World Computer Shogi Championship, the report said.
Playing without handicaps, Sato had the upper hand until the middle of the game, when he began making mistakes.
The first of the five games at this year's competition was won by shogi pro Koru Abe against a different programme, the report added.
According to the report, the third episode of the contest is set for April 6.