Allegations of software-assisted cheating by top-ranked shogi (Japanese chess) player Hiroyuki Miura led to his suspension from competition earlier this month, but a lack of hard evidence and a dubious investigation process has left more questions than answers about the controversial decision.

The stunning call by the Japan Shogi Association to suspend Miura was issued Oct. 12, just three days before the opening of the seven-game Ryuo championship battle where he would have faced title holder Akira Watanabe.

The play of Miura, a 42-year-old holder of the ninth dan, the highest of the game’s current ranking, had been drawing attention from opponents over recent months after what they considered odd behavior, including leaving his seat during matches more often than usual, raising suspicions of cheating.

The players suspected Miura may be using software running remotely and accessed via a smartphone, in violation of shogi rules. Using a smartphone, it is possible to access a program on a PC to find out the next most effective move.

Players of the chess-like game have become wary of fellow competitors’ behavior since the development of powerful shogi software that often beats the world’s best players.

On Oct. 10, Watanabe, the holder of the ryuo (dragon king) title, who had grown suspicious of Miura during past matches, met six other top players behind the scenes to investigate cheating allegations, according to a shogi association source.

They included Koji Tanigawa, a ninth dan who heads the association, Akira Shima, a ninth-dan association executive, and Shota Chida, a fifth dan known for his expert knowledge in shogi programs. Miura was not invited as his rivals began their back-room sleuthing.

In the meeting, data was shown indicating Miura’s moves regularly matched what software would recommend, the source said.

After the investigation, Watanabe resolved to withdraw from the upcoming tournament, saying he has no intention of playing against someone with cheating suspicions hanging over them, according to the source. He made the alleged remark aware that the decision may lead to him being stripped of his title.

The following day, the federation questioned Miura, with Watanabe present. Miura denied cheating, explaining that he left his seat in order to take a break in another room. He nonetheless offered to skip the imminent tournament, saying he would not play while his integrity was being questioned, the federation said.

Despite handing down the ban, the association has been able to come up with only circumstantial evidence in Miura’s case, failing to table any hard proof of cheating. It will, however, soon set up a team of lawyers to continue investigations.

After vowing that he would not play at the tournament, Miura failed to officially withdraw, leading to the federation’s Oct. 12 suspension, which lasts through the end of the year.

Miura, however, challenged the decision, issuing a statement through a lawyer categorically denying the use of software during matches.

He also said he presented images showing all software on his PC and smartphone. But “the federation did not scrutinize any of these documents before handing down a unilateral penalty,” he said.

Shogi software has become increasingly sophisticated. Every year since 2012, pro players have taken on computer programs with humans winning only five times, the software 12 times and one draw. Miura was one of those beaten by a computer opponent in 2013.

The general perception is that shogi programs are now equal to — or better — than professional players, many of whom use software for training.

The game’s governing association has no specific rules about a player leaving his seat during play as it was generally left to an honor system that trusted professional players to not cheat.

But with an increasing number of players calling for a change, the association announced Oct. 5 that it is banning players from bringing smartphones to play areas and also from leaving the Shogi Kaikan building during play.