Stone Age Idle and the 'Kiugi' Craze: Why Korea's Biggest Publishers Now Make Games You Don't Play

There is a word every Korean mobile gamer knows in 2026: kiugi, "raising". Put it after almost any famous name, and you have a genre. Mushroom raising. Maple raising. And since March, Stone Age raising.

Stone Age Idle, Netmarble's new idle RPG, launched on March 3, 2026. It topped the popularity chart on Apple's Korean App Store within eight hours and on Google Play within two days, then settled at No. 2 in Apple's grossing chart and No. 14 on Google Play in its first days, inews24 reported. Byline Network later counted it at No. 4 in Korea's top-grossing ranking. It is the clearest sign yet that Korea's largest publishers have fallen for a genre they once left to tiny studios.

What a kiugi game is

An idle RPG plays itself. Your heroes fight automatically and keep earning experience and loot even while the app is closed. Your job is to make decisions: which skills to upgrade, which gear to equip, when to push a harder stage. Sessions are short and frequent, which is the point.

Stone Age Idle applies that formula to Netmarble's long-running Stone Age world of cave people and pet dinosaurs, an IP that Netmarble says has reached 200 million players worldwide. It is not even Netmarble's first try: the company launched Seven Knights Idle Adventure in 2023.

The king of kiugi

The game Stone Age Idle is chasing is MapleStory: Idle RPG from Nexon. Launched on November 6, 2025, it passed $100 million in revenue in 45 days and, according to Sensor Tower, about $430 million within 11 months. It stayed No. 1 on both Korean app stores' grossing charts in March 2026, even after Nexon offered a full refund over a hidden probability error earlier in the year.

MapleStory: Idle RPG also shows how players actually use these games. Sensor Tower found that its players open it about seven times a day for about 12 minutes each time, both the highest among top-grossing idle RPGs.

Why Korea loves games that play themselves

inews24 and the market reports it cites point to a few reasons:

• Less time, same appetite. Players have less time for games but still want progress, so a game that needs minimal operation fits busy lives.
• The short-form effect. As short videos have taken over how people spend spare minutes, quick, compressed fun competes better than long sessions. A Byline Network source made the same comparison in March, noting that compact games are now preferred to heavy ones.
• Familiar names. Almost every big Korean idle hit is built on a well-loved IP, so players arrive with nostalgia already in place.

The money is real too. Market research cited by inews24 put the global idle game market at about $2.5 billion in 2024, with forecasts of growth to about $6.1 billion by 2033, and the Asia-Pacific region expected to grow fastest.

What's next

With Nexon and Netmarble both scoring idle hits within six months of each other, expect more famous Korean names to get the kiugi treatment. WGC's take: idle RPGs are sometimes dismissed as barely games, but they have become one of the most reliable ways for Korean publishers to bring an old IP back to life. The challenge will be standing out once every classic has its own raising game, and keeping players' trust over monetisation, a lesson MapleStory: Idle RPG learned the hard way in January.