This initial clinical trial evaluated the efficacy and safety of the retrograde intrarenal surgery using the robotic flexible ureteroscopy system, Zamenix R, in a multi-center, prospective, single-arm study. A total of 47 adult Korean patients with one or more kidney stones, ranging in maximal size from 5 to 30 mm, were recruited, and 46 patients were included in the analysis. The median age of patients was 57.50 [IQR 48.25-63.00] years, with a median of 1.00 [IQR 1.00-2.00] stones per patient and a median maximal size of 13.70 [IQR, 10.00-16.00] mm and a volume of 349.65 [IQR 201.60-704.10] mm³. The stone-free rates were 93.48% (< 4 mm), 71.74% (< 2 mm), and 56.52% (zero stone), based on each respective stone-free definition, with no conversions to conventional surgery. The median operative time was 91.50 [IQR 64.25-113.75] minutes, with a median console time of 71.00 [IQR 39.25-92.75] minutes. Ureteral injuries occurred in 17.39% of cases, including 6.52% Grade I and 10.87% Grade II injuries, all related to manual insertion of a ureteral access sheath. The postoperative complication rate was 6.52%, with all cases being Grade II urinary tract infections. Laser ablation speed was higher for larger stones. The operators reported low levels of musculoskeletal fatigue and numbness. The results demonstrated the efficacy and safety of the robot-assisted flexible ureteroscopic surgery using Zamenix R. Further investigation is required, including a comparison with the standard of care and a larger sample size.