Evaluate the Efficacy and Safety of KK8398 in Patients With Achondroplasia（AOBA Study）

Inclusion Criteria: 1. Patients who are between 2.5 and 17.5 years old of age at the time of provisional registration. Patients who meet certain criteria in terms of Tanner stage and bone age. 2. Patients who have been diagnosed with achondroplasia through genetic testing. Exclusion Criteria: 1. Patients who meet the criteria for a certain height determined by age and gender in the "Growth Chart for Patients with Achondroplasia" at the time of the pre-registration examination 2. Patients who have received treatment with r-hGH or a CNP analogue within a certain period prior to the pre-enrollment examination. 3. Patients who have had previous osteotomy or who are scheduled to undergo osteotomy or epiphyseal growth inhibition during the study period. Epiphyseal growth inhibition in which the plate was removed more than 26 weeks prior to the pre-registration examination will not be excluded if the patient has completely healed without sequelae, based on the judgment of the investigator or sub-investigator.