The scintillator-based fast-ion loss detector (FILD) project in Japan, Korea, and China has been accelerated in an international collaboration framework to enhance comprehensive understanding of fast-ion behaviors in toroidal fusion plasmas. The FILDs in LHD heliotron, KSTAR, HL-2A, and EAST tokamaks are successfully working as a result of joint work. Physics experiments on fast ions, such as effects of Alfvénic mode, tearing mode, resonant magnetic perturbation field, and disruption on fast-ion behaviors are ongoing. This paper describes the FILD developed for each device and those effects on fast ions in LHD, KSTAR, HL-2A, and EAST.