Double Dutch is a sport in which jumpers perform various tricks while jumping through a rope spun by two turners standing facing each other. Moves include running jumps at double speed, moves where the turners spin the rope while moving sideways, and moves where jumpers switch places with the turners mid-jump. Recently, it seems that many universities have Double Dutch clubs.
“Double Dutch” and “DOUBLEDUTCH” are registered Japanese trademarks (Nos. 3366188 and 3366189) in standard characters, with “sports equipment” designated as the goods covered.
https://www.j-platpat.inpit.go.jp/c1801/TR/JP-1995-059878/40/en
https://www.j-platpat.inpit.go.jp/c1801/TR/JP-1995-059879/40/en
Note that the trademark owner, the Japan Double Dutch Association (a specified nonprofit corporation), was integrated into the Japan Jump Rope Federation (a general incorporated foundation) in 2021.
In addition, Japanese Utility Model Registration No. 3149031 discloses a design for a jump rope training device well-suited for Double Dutch practice. When using this training device, even if the turner is a beginner, the middle section of the rope does not sag but forms a smooth arc, making it easier for jumpers to time their entry into the rope. While tools can be helpful, the key is consistent practice. (Conan)