Shining Arcs Tokyo Bay Urayasu suffered shock relegation to League One's Division 2 on Saturday in a 33-19 loss to the second-tier Sagamihara Dynaboars.
Having lost last week's first leg 33-25, the Shining Arcs needed to win by at least eight for any chance of survival at Osaka Prefecture's Hanazono Rugby Ground, but were unable to pull it off as the Dynaboars earned promotion to Division 1.
In March, telecommunications company NTT said NTT Communications Shining Arcs Tokyo Bay Urayasu would become the company's primary League One entry from next season.
Its other club, NTT Docomo Red Hurricanes Osaka, finished the regular season a place below the Shining Arcs in 11th. But with the Red Hurricanes' drop to Division 3 as a club based around company employees having already been decided, the Shining Arcs played Division 2's third-place Dynaboars.
The Shining Arcs got off to a promising start when former Australia star Israel Folau threw his body forward to provide a pass to wing Kai Ishii to cross down the left in the 10th minute.
The Dynaboars scored five minutes later after a quick restart from scrumhalf Kota Iwamura sent Matt Vaega past the disorganized Shining Arcs defense, with the fullback adding the extras.
Defensive errors put the Shining Arcs in further trouble 12 minutes later as the Dynaboars retrieved a punt deep in their opponents' half. Center Michael Little's diagonal punt bounced beyond the reach of a Shining Arcs player before Takumi Sugiura grounded it for a try.
Folau was responsible for the Dynaboars' 38th-minute try, failing to catch a ball deep in his own half as wing Sugiura, an eighth-minute substitute, scored his second try.
Shining Arcs hooker Sekonaia Pole scored straight off the bench from a maul three minutes after the first-half hooter as they went into the break trailing 19-12. But successive penalties conceded at breakdowns and lineouts took the wind out of their sails in the first 20 minutes of the second half.
The squad boasting Folau, former Super Rugby star Otere Black and 41-year-old former Japan lock Luke Thompson played the majority of the stanza in the opposition half until a pass from Black was intercepted for Dynaboars center Nozomi Nara to run three-quarters of the pitch to score between the posts.
Vaega converted for a 26-12 lead with 12 minutes to go and the Shining Arcs, without former Scotland captain Greig Laidlaw, scored a consolation try off a scrum from Shuhei Takeuchi.
Dynaboars scrumhalf Ealey Nicholas Ealey capped the victory with a try from a charged-down kick as his team celebrated promotion in style.
In Division 1's third-place playoff, Hiroyuki Yamasaki scored two first-half tries as Spears Funabashi Tokyo Bay held off Brave Lupus Tokyo 23-15.
The wing's 27th— and 38th-minute tries helped the Spears end the regular season on a winning note after they lost their playoff semifinal to Saitama Wild Knights last weekend.
"It was fierce at the breakdowns. I'm glad to have scored two tries, and our forwards worked their socks off," said Yamasaki after his side bounced back from a difficult start at Prince Chichibu Memorial Rugby Ground.
Two tries from wing Yamasaki helped the Spears come from 12-0 down and lead 17-15 at the break.
Penalties by Bernard Foley in the 49th and 67th minutes extended the lead as the Brave Lupus, who without Japan back-row forward Michael Leitch and former All Black Matt Todd, were unable to score a single point for the final 44 minutes.