Competitors must walk across forty foam dominoes of increasing height and sensitivity (the further along the competitors went, the less stable the dominoes would become), without losing their balance. The distance of the obstacle itself is eighteen meters.
This was one of the most iconic obstacles in KUNOICHI, and also one of the most difficult, as it has the lowest success rate of any obstacle in KUNOICHI history.
KUNOICHI 3-6 Version
The first incarnation of the Tourenban lasted for four tournaments. It was comprised of a grand total of forty foam dominoes, split into four zones, each zone taller and thinner than the last.
- The first zone, the blue zone consisted of twelve dominoes, all at the same height. It was roughly one meter high.
- The second zone, the green zone, consisted of eight dominoes. The first half of this zone had it's dominoes at about 1.25 meters high, while the second half raised the height to 1.5 meters.
- The third zone, the yellow zone, was modeled exactly like the green zone; however, the height of the dominoes was increased to 1.75 meters and 2 meters.
- Finally, the red zone was the final section of the Tourenban. It was composed of twelve foam pieces, the first half at 2.25 meters, the second half at 2.5 meters, and the last half at 2.75 meters.
The yellow and red zones were the most lethal portions of the obstacle, accounting for fourteen out of sixteen failures. Using hands during this obstacle was not allowed, demonstrated by Iwai Tomoka in KUNOICHI 6.
KUNOICHI 7 Version
The second version of the Tourenban was similar to the first; however, the red zone had been replaced with ten rounded posts, somewhat similar to the Buyoishi known as the Tourenbou (倒連棒), which is considered as an individual obstacle not part of Tourenban, as the third obstacle of the stage.
In addition, each zone now had ten dominoes a piece instead of the twelve-eight-eight-twelve format. Though, not much is known about the new red zone since no one attempted it; however, it looked as if the red zone was potentially spring-loaded, or had the potential to move much more than the original red zone, making it much harder for competitors to traverse.
KUNOICHI 8- Version
The third and final version of the Tourenban was toned down in the course redesign of KUNOICHI 8. It was placed as the fourth obstacle in the Second Stage and was composed of seventeen foam dominoes, all about 1.5 meters in height. Unlike the original Tourenban, the top of the foam pieces had their edges cut off, possibly to keep competitors in a straight line, making the obstacle harder to traverse. Due to its modification and stage relocation, the number of completions in this tournament was much higher than the previous tournaments.
This version would eventually return for KUNOICHI 9, where it was identical to the version from the previous tournament, aside from an aesthetic colour change. It was still placed as the fourth obstacle in the BLUE Stage (Second Stage) and was renamed as the Sponge Bridge (スポンジブリッジ) (which also the name of an event in Kinniku Banzuke, in which this obstacle was inspired from). The number of foam dominoes was reduced to fifteen. Only one out of five competitors could complete it.
The Sponge Bridge returned once again in KUNOICHI 10, where it was the third obstacle in the BLACK Stage (Third Stage). This time, among the three competitors who attempted the obstacle, all of them could complete it (making it the first time in KUNOICHI history that the Tourenban/Sponge Bridge had a 100% completion rate).
In KUNOICHI 11, all competitors cleared except Tsubuki Airi, when she used her hands and got disqualified.
American Ninja Warrior
KUNOICHI 8 version of the Tourenban (called as the Domino Hill) appeared on American Ninja Warrior 5, as the third obstacle in Venice Beach, becoming the first KUNOICHI obstacle to be used on American Ninja Warrior (since American Ninja Warrior was mostly based on SASUKE).
In this version, there were only seven dominoes instead of seventeen. In addition, the dominoes were at a gradual incline.
Unlike in KUNOICHI, where competitors took a slow approach to complete it, most competitors used a fast approach by skipping some dominoes.
SASUKE Ninja Warrior Indonesia
The Domino Hill also appeared on SASUKE Ninja Warrior Indonesia, as the third obstacle during Challenge Stage, becoming one of the most iconic obstacles of the stage.
In this version, the obstacle was more similar with KUNOICHI 3-6 version, except the number of dominoes was drastically reduced to just eleven, and all dominoes had the same height.
Competitors were not allowed to touch the obstacle with their hands, not step the top of the dominoes, and skip the dominoes (i.e. not step all of the dominoes). This version of the Domino Hill was proven to be relatively easy for the competitors.
Ultimate Domino Hill
On SASUKE Ninja Warrior Indonesia 2017, the Domino Hill returned in the form of the Ultimate Domino Hill, once again as the third obstacle during Challenge Stage.
This time, the obstacle was more similar with the KUNOICHI 8 version, except there were eleven equally-sized dominoes arranged on a staircase.
Competitors were not allowed to touch the obstacle with hands, skip the dominoes (i.e. not step all of the dominoes), and touch/step the padding.
Unlike on the previous season, several competitors (including rookies and veterans) failed on this obstacle, in which most of them failed to maintain the balance.
In the end, the Ultimate Domino Hill became the cut-off for advancing to Warrior Stage, in which the position of the domino that could be reached by competitors (first through eleventh) and how fast competitors could reach that particular domino would determine whether competitors advanced to Warrior Stage or not.
During SASUKE Ninja Warrior Indonesia: International Competition, the Ultimate Domino Hill caused chaos, as notable competitors from different teams were taken out by this obstacle (due to the fact that competitors tried to complete the course in the fastest possible time, resulting some competitors were disqualified for skipping some of the dominoes). Competitors who fell at this obstacle during the tournament were:
- Drew Drechsel and Josh Levin from Team USA,
- Dion Trigg and Sergio Verdasco from Team Europe, and
- Hioki Masashi, Kawaguchi Tomohiro, Morimoto Yūsuke, and Matachi Ryo from Team Japan.
Competitors' Success Rate
- All results based on the TBS broadcast and external information found