Background A loot box is a gaming term for an electronic lottery that randomly provides items that enhance the gaming experience. In recent years, loot boxes have been increasingly discussed as a risk factor of gaming disorder (GD). While they may be purchased for a few dollars at a time, the cumulative expenses resulting from their addictive use have become a social problem. Case Presentation This paper presents a case of GD involving a substantial financial burden incurred through the use of a Japanese loot box called Gacha. Conclusion The randomness in the selection of virtual items in loot boxes resembles gambling, triggering the reward system and contributing to an addiction to purchasing more loot boxes. For therapeutic purposes, understanding the motivations behind purchasing loot boxes and considering individual developmental characteristics are crucial to helping patients find satisfaction and a sense of achievement in activities besides gaming.