In-game purchases, including microtransactions and loot box spending, are the monetization systems of free-to-play online games. 4Faculty of Health and Welfare, Kawasaki University of Medical Welfare, Kurashiki, Japan.3Faculty of Business Administration, Hokkai-Gakuen University, Sapporo, Japan.2School of Education and Culture, Hokusho University, Ebetsu, Japan.
1Research Center for Child Mental Development, Graduate School of Medicine, Hirosaki University, Hirosaki, Japan.Hiroki Shinkawa 1* Tomonari Irie 2 Masanori Tanaka 3 Kengo Yokomitsu 4
