The 3DS eShop closed permanently in March 2023. Double Cross (JPN) is no longer legally purchasable digitally. For archivists, dumping their own physical cartridge to a ROM (using homebrew like GodMode9) is the only way to preserve the software for future generations.
To understand the double naming, we must look back at 2015. Monster Hunter X (pronounced "Cross") was released in Japan as a celebration of the series' 10th anniversary. It introduced (Guild, Striker, Aerial, Adept) and Hunter Arts —special super moves. The West received this game as Monster Hunter Generations . monster hunter xx double cross 3ds rom jpn