In 2004, J. League introduced a series of two test matches called League (J1/J2 play-offs) between the sixteenth-place J. Division 1 (J1) club and third-place J.league Division 2 (J2) club. The winner of this game receives the third and final ticket to J1 in the following season, with the first two going to the first- and second-place J2 teams at the end of the season.
Prior to 2004, promotions and relegations involved the two bottom J1 clubs (15th place & 16th place) and two top J2 club (1st & 2nd places). At the end of the 2004 season, J1 expanded from 16 clubs to 18 clubs. Due to the expansion, the league promoted the top two teams in J2 to J1 without any relegations. The league also instituted a new playoff game that allowed the 3rd-place J2 club to challenge the 16th (and at the time, last-) placed J1 club for a berth in J1 in the 2005 season. This was the start of this promotion/relegation Series. After the expansion, the league went back to their standard promotion and relegation system (17th & 18th in J1 switching places with 1st & 2nd in J2), but the promotion/relegation Series continued. The final series is the 2008 edition, as this is the final year J2 will have been composed of fewer than 18 teams. From 2009, direct promotion and relegation will be in place for three clubs of each division.
The irekae-sen concept is not new; it was a feature of the original Japan Soccer League, when, until 1980, it was usual that the bottom two team(s) in the First Division played off against the winner and runner-up of the All Japan Senior Football Championship and, after 1972, the Second Division's top two. After 1980 only the second-from-bottom team played against the Second Division runner-up.
In 2012 the irekae-sen concept was revived for the purpose of promotion and relegation between J2 and the Japan Football League, but it will be conditional on JFL clubs having J. League Associate Membership. Following the creation of the J3 League, the playouts remained until 2015 when promotion for the top two places was automated, conditional on clubs having J2 licences.
J2 clubs are only allowed to be promoted if they fulfill the J1 promotion criteria.
In practice, given the more stringent rules for promotion from JFL to J2, these rules can be considered a mere formality.
| Year | J.League Division 1 16th-ranked | Score | J.League Division 2 3rd-ranked | |
|---|---|---|---|---|
| 2004 | Kashiwa Reysol | 2–0 2–0 4–0 agg. | Avispa Fukuoka | |
| 2005 | Kashiwa Reysol | 1–2 2–6 3–8 agg. | Ventforet Kofu | |
| 2006 | Avispa Fukuoka | 0–0 1–1 1–1 agg. (away: 0–1) | Vissel Kobe | |
| 2007 | Sanfrecce Hiroshima | 1–2 0–0 1–2 agg. | Kyoto Sanga | |
| 2008 | Júbilo Iwata | 1–1 2–1 3–2 agg. | Vegalta Sendai |
In the first year of this series, Kashiwa easily held their position in J1 by defeating Fukuoka in the series with aggregate score of 4–0.--------Kashiwa Reysol won 4–0 on aggregate and remained in J.League Division 1.
Avispa Fukuoka remained to J.League Division 2.----
In the years prior to 2005, Ventforet Kofu were facing extinction due to losing money running into hundreds of million yen. Having finished bottom of J2 for three seasons in a row, in 2002 the club hired Kazuyuki Umino as the president who was able to turn the club around. The club started to make profit, attendance increased, and the club's performance improved each year. Finally, after defeating the J2 champions Kyoto Purple Sanga on the final matchday of 2005, they managed to finish in third place.
Kashiwa Reysol on the other hand, finished 16th and had to play this series for two seasons in a row. Many believe Kashiwa underestimated this series as they easily defeated Avispa Fukuoka last year.
The irony was that on December 7, 1969, exactly 36 years before, Venforet Kofu's forerunner the Kofu Club, played and lost in promotion/relegation Series (JSL, at the time a single division, against the two finalists of the Shakaijin Cup; Kofu had been runner-up) against the Hitachi Club (Kashiwa Reysol's previous affiliation), who had finished 7th of 8 in the old league. Before the 2005 series, and excepting the 1973 season when as JSL Division 2 runners-up they lost another series at the hands of now-defunct Nippon Kokan, this had been the closest Kofu came to competing in the top division.
In the final minutes in the first leg, the Kose Sports Stadium blacked outed and the game was stopped. The lights came back after 20–30 minutes. In the second leg of this series, Bare had managed to score double-hat-trick (6 goals), which is a record for any J.League competitions until Michael Olunga scored 8 goals in a match on 24 November 2019 (2019 J2 League).
See 2005 J.League Division 1 for details.
--------Ventforet Kofu won 8–3 on aggregate and promoted to J.League Division 1.
Kashiwa Reysol relegated to J.League Division 2.----
From matchday 28 it was clear that the relegation battle was limited to three clubs; Kyoto Purple Sanga, Cerezo Osaka, and Avispa Fukuoka. All other clubs officially passed the relegation line by matchday 32. Kyoto were relegated on the penultimate week of the season. Gpoing into the final week, Cerezo Osaka (16th) were one point head of Fukuoka (17th). Osaka lost as Fukuoka drew, meaning they finished level on points. However, Avispa clinched the 16th place on account of their superior goal difference of -24 as opposed to Cerezo's of -26.
The same situation was occurring in the J2 promotion race, with three clubs, Yokohama F.C., Kashiwa Reysol, and Vissel Kobe way ahead of other clubs, but only two automatic promotion sports available. In the penultimate week of the season, Yokohama clinched the championship and promotion. Heading into the final matchday, Kobe sat in 2nd, one point ahead of Kashiwa, and it appeared that Kashiwa would have to settle for the playoff series for the third year running. However, on the final day of the season, Kashiwa won and clinched the runners-up spot after Kobe fell down to third place by losing the last match.
The Series finished 1–1 on aggregate following a 0–0 draw in the first leg but Kobe won on the away goals rule and replaced Fukuoka in the first division.
See 2006 J.League Division 1 for details.
--------1–1 on aggregate. Vissel Kobe won on away goals and promoted to J.League Division 1.
Avispa Fukuoka relegated to J.League Division 2.----
In 2007, Kyoto Sanga FC defeated Sanfrecce Hiroshima 2–1 on aggregate to clinch a spot in J1 for the 2008 season. Hiroshima are relegated to J2 for the first since 2003.
See 2007 J.League Division 1 for details.
--------Kyoto Sanga won 2–1 on aggregate and promoted to J.League Division 1.
Sanfrecce Hiroshima relegated to J.League Division 2.----
The last promotion/relegation series for the time to come featured, as in the first edition, the higher division club saving its position in J1. This was the first time since 1980 that Júbilo Iwata (then known as Yamaha Motors) had to battle to keep its position in the top division; in 1980 they had defeated Fujitsu, the forerunner to Kawasaki Frontale.
See 2008 J.League Division 1 for details.
----Júbilo Iwata won 3–2 on aggregate and remained in J.League Division 1.
Vegalta Sendai remained in J.League Division 2.