Fourth-place Yokohama Eagles and sixth-place Toyota Verblitz won their respective matches Sunday, the last day of the Japan Rugby League One regular season.
With the top four teams having already secured their playoff berths, Eagles scored four tries in each half to overwhelm Kobe Steelers 52-26 at Hanazono Rugby Stadium.
Eagles saw their big early lead cut to 26-19 five minutes into the second half, but tries from Chihito Matsui and Shin Kawamura put the contest back in their control.
The Yokohama-based club finished the season with a 10-4 win-loss record with two draws.
At Yamaha Stadium, visiting Verblitz held on for a 37-27 win over Shizuoka BlueRevs thanks to a pair of first-half tries by Rob Thompson.
Tokyo Sungoliath fullback Seiya Ozaki finished as the league's top try scorer with 18, while Spears Funabashi Tokyo Bay flyhalf Bernard Foley's 173 points were the most by any player.
In the semifinals, Eagles will play defending champions and top seeds Saitama Wild Knights on May 13 before Spears and Sungoliath meet the following day.