A Tokyo man has been arrested on suspicion of long-term child abuse involving his ex-girlfriend's twin 8-year-old sons.

Shuji Tomohiro, 35, is accused of throwing the boys, then 7 years old, into bushes in front of his house in Fuchu on Nov. 16, 2015. One suffered broken teeth in the incident.

Tomohiro, a bodybuilder, admitted to the allegation but said he did not intend to do harm to the boys, who reside in nearby Akishima. He said the incident happened as "part of sports practice," investigative sources said.

The other boy was not injured in the 2015 incident but was hospitalized months later, on April 3, 2016, for a subdural hematoma that saw him temporarily fall into critical condition, police said.

Tomohiro once won a bodybuilding prize, and neighbors often saw him training the twins, who were members of the track and field team, making them run and do pushups.

Investigators said that after Tomohiro began dating their mother around August 2015, the boys' elementary school teacher began to see scars and bruises appear on their bodies. When questioned by the teacher, the boys reportedly said they got them while practicing at a gym.

The arrest came after a relative told police that the boy had been with Tomohiro at a park when he collapsed and was taken to the hospital unconscious.

Tomohiro reportedly told the police before he was arrested that he didn't see the boy collapse, claiming that he came back from the toilet and found the boy on the ground. Since the boy did not have any external injuries, police believe he might have been rendered unconscious by a strong jolt.