IgA nephropathy (IgAN) is a chronic progressive kidney disease, and long-term control of proteinuria and prevention of relapse are crucial for delaying disease progression. Patients with IgAN who achieve proteinuria remission after receiving Nefecon for 9 months or longer still face the risk of proteinuria relapse after treatment discontinuation. This study is to evaluate the efficacy and safety of Nefecon 8 mg treatment for 15 months as a maintenance therapy for prevention of proteinuria relapse in proteinuria-remitted patients.