A 29-year-old employee, who was inspecting the S&S roller coaster, got caught between a stopped vehicle and rail, and later died at a local hospital. The employee was part of an 11-man team inspecting the ride, which was closed for the day and not in operation at the time of the incident. Source (in Japanese)
Although it’s not an accident, a 14-year-old boy died after suffering a heart attack during a school trip to the park. The incident occurred when the student started feeling uneasy, sat on a bench, and collapsed on the ground. Source
A 13-year-old girl was injured after being ejected from the Chance Rides spinning Trabant-style attraction. Source