The eldest of three teenagers charged in the killing last year of a 13-year-old boy on a riverbank in Kawasaki pleaded guilty Tuesday to assault and murder.

The 19-year-old boy, whose name is being withheld due to his age, is the suspected ringleader in the February 2015 slaying of Ryota Uemura.

The case is being heard in the Yokohama District Court by three professional and six lay judges.