Canon Eagles became the fourth and final side from Group B to confirm their spot in the LIXIL Cup, the playoff tournament for the Top League.
On Sunday, the Eagles defeated Toyota Industries Shuttles 35-19 to go third in the standings on 21 points, three behind group leaders Yamaha Jubilo.
With just two games remaining in the regular season, the top four sides — Yamaha, Toyota Verblitz, Canon and Kobe Kobelco Steelers — cannot be overtaken by the side currently in fifth, NTT Docomo Red Hurricanes.
Naoki Moriya was named man-of-the-match after scoring a try and kicking five second-half conversions, while former All Blacks flanker Adam Thomson, Springbok fullback Willie le Roux, Kosuke Hashino and Ryota Suginaga also crossed the whitewash for the Eagles, who triumphed despite playing for 20 minutes with 14 men after having two men sent to the sin bin.
While the top four finishers in Group B have been determined, Group A is a far tighter affair with five teams still in contention for the four playoff spots.
This year's competition has been abbreviated because of the Rugby World Cup and Japan's first venture into Super Rugby starting in February.
Each team will play just seven group-stage games through Dec. 26 with the best four teams from each of the two eight-team groups squaring off in the playoffs for the league championship, and the final taking place on Jan. 24.