Lysosomal storage diseases (LSDs) (designated intractable diseases 9) are congenital metabolic disorders that cause systemic symptoms, including central and peripheral symptoms, due to the excessive accumulation of substrates in the lysosomes of various organs. LSDs are caused by latent genetic mutations of lysosomal enzymes and auxiliary factors, resulting in a deficiency of enzyme activity. More than 50 types of LSDs are known, and so far, enzyme replacement therapy (ERT) has been clinically applied to LSDs [1]. ERT is a fundamental treatment based on the principle of decomposing accumulated substrates by utilizing the physiological function of N-glycans specifically added to lysosomal enzymes. In recent years, the clinical development of gene therapy (GT) based on cross-correction, which introduces therapeutic enzyme genes directly into the patient’s body using vectors such as adenovirus (AAV) or lentivirus (LV) or by transplanting cells introduced from outside the body, has been progressing.