Lock Walt Steenkamp and winger Ben Paltridge each scored a brace of tries to lead Sagamihara Dynaboars to a 34-28 upset win against defending Japan Rugby League One champions Kubota Spears on Sunday.

In a see-sawing contest, Steenkamp edged the Dynaboars ahead 29-28 in the 70th minute before player of the match Paltridge extended the margin with his second try at Prince Chichibu Memorial Rugby Ground.

The result snapped a three-game win streak for Kubota, who remained outside the playoff picture in sixth place.

Sagamihara's victory came despite kicking difficulties for playmaker James Grayson, who missed two penalties and converted just two of his team's six tries.

The Dynaboars opened the scoring after Jackson Hemopo caught Grayson's kick pass and offloaded for Masataka Tsuruya to go over.

Kubota quickly hit back when Dane Coles grabbed a loose ball and made ground before sending Faulua Makisi over with a one-handed pass.

Spears captain Harumichi Tatekawa's kick pass set up Haruto Kida's converted try for a 12-5 lead midway through the half, but the same tactic backfired in the 40th minute, when Paltridge intercepted and scored to leave the game deadlocked 17-17 at the break.

In Sunday's other match, All Blacks flanker Ardie Savea spurred Kobe Steelers to a 57-22 rout of Toyota Verblitz with a four-try performance at Hanazono Rugby Stadium.