Kien was originally developed between 2002 and 2004 by AgeOfGames, a group of five Italian developers who had no prior experience making video games, aiming to be the first company in their country to develop a game for the Game Boy Advance. The game's release would end up being cancelled three separate times when multiple publishers picked up the game and then decided that releasing it would be too risky for sales. At the time, the game was completed and sent to gaming publications, with one known review appearing in the American magazine Nintendo Power in 2003. The game remained unreleased for over 20 years, but a prototype ROM of it did leak online at one point. Game designer Fabio Belsanti would be the only member of the game's original development team to remain at AgeOfGames, who had shifted to developing educational games to stay afloat. Eventually, with the rising popularity in retro games and lowered cost to produce GBA cartridges, AgeOfGames was able to release Kien in 2024 both digitally and on physical cartridges through retro game publisher Incube8 Games. The game's release garnered attention for it possibly having taken the record for the longest delayed video game release in history, surpassing Duke Nukem Forever and Beyond Good & Evil 2 by taking 22 years to release.