This study aimed to clarify the human casualties of the earthquake that struck the city of Osaka at 7:58 on the morning of June 18, 2018, for which a maximum seismic intensity of lower-6 was recorded at the epicenter in the northern part of Osaka Prefecture, based on the callout records of the Osaka Municipal Fire Department. By identifying the casualties directly attributable to the earthquake based on human characteristics, injuries, and other factors, this study is expected to prompt renewed acknowledgment of previously ignored risks lurking in daily life. According to the changes over time, both earthquake-related endogenous injuries, such as dizziness and respiratory distress, and exogenous injuries, such as trauma, peaked between 8:00 and 9:00 or between 11:00 and 12:00, and subsided by 12:00. The casualties consisted of eighteen men and thirty women, with most individuals aged in their 80s. Exogenous injuries were more common in both older men and women, whereas endogenous injuries (joint disorders, cardiovascular and respiratory system disorders, general symptoms and signs, and cognitive, sensory, and emotional states and behaviors) accounted for a high proportion of the injuries in girls/women aged 10–29 years.