The Top League will undergo yet another change next season, as the Japan Rugby Football Union tries to give Super Rugby side the Sunwolves more preparation time amid concerns for the welfare of the nation's top players.
The 2017-18 season, which is set to start on Aug. 18 and finish on Jan. 14, sees the 16 teams split into two conferences.
Teams will play the seven other sides in their own conference plus six from the other to determine the rankings for the playoffs.
The top four sides will compete for the league title, which doubles up as the All-Japan Championship which no longer involves university teams. There will be similar four-team playoffs for all the other positions, with the side finishing 16th automatically relegated to the new national second division, the Top Challenge League.
The sides finishing 13th to 15th will play promotion/relegation games against the second- to fourth-ranked teams from the second division.
"Our first priority is to contribute to the development of the Japan national team," said Top League commissioner Osamu Ota.
"We talked with (Brave Blossoms coach) Jamie Joseph, (national team director) Masahiro Kunda as well as the 16 teams and created this new format."
Ota said a reluctance from some teams to play when the Brave Blossoms are away in November or to play midweek games, and the need to finish in mid-January, helped shape the new competition, which will be in place for at least the next two seasons.
In the past, the league has featured a straight round-robin format, a round-robin followed by playoffs, a two-stage, two-group competition followed by playoffs and a shortened two-group competition followed by playoffs.
"The teams wanted a round-robin format but also wanted some time off in the season for reconditioning," Ota explained. "We also wanted to give the Sunwolves at least five weeks before they played their first game."
Conference A, as it is being called for the time being, will feature Suntory Sungoliath, Kobe Kobelco Steelers, NTT Communications Shining Arcs, Toyota Verblitz, Toshiba Brave Lupus, Kubota Spears, Kintetsu Liners and newly promoted NTT Docomo Red Hurricanes.
Yamaha Jubilo, Panasonic Wild Knights, Ricoh Blacks Rams, Canon Eagles, NEC Green Rockets, Munakata Sanix Blues, Coca-Cola Red Sparks and Toyota Industries Shuttles will make up Conference B.
"The teams have been grouped according to how they finished this past season," Ota said, with the same process applying for the 2018-19 season.
"There was a lot of talk about who should play who in the inter-conference games, and we eventually decided to do it based on ranking."
As such, the 2016-17 champions Suntory, for example, will not play Coca-Cola and Toyota Shuttles, the two lowest-ranked sides in Conference B.
Ota said that from a national team viewpoint the league season needed to be shorter in order to give Japan's top players a break given their commitments to the Sunwolves and the Brave Blossoms.
"Jamie Joseph has said 32 games should be the limit," Ota replied when asked how many games a top Japanese player should play in a season.
"But there has to be equality. There will be no set rule and there will be flexibility but the company teams wanted a round-robin so this format is the one that works best."
Ota said in future years the number of teams in the Top League could be reduced and the Top Challenge League expanded. There were also ongoing talks about whether universities should be included and whether students could play both for their schools and a Top League side.
At present, players cannot be registered to play for two teams, so Takuya Yamasawa had to give up playing for University of Tsukuba so he could play for Panasonic in the recently completed Top League season.
"For the next two seasons, there will be no change in the league format," Ota said. "As to whether students can play in the Top League (when their universities have no game) depends on the companies and other factors such as insurance. But it could happen next season."