A 27-year-old man pleaded guilty yesterday to fatally stabbing his neighbor at the Makaha Valley Plantation in March during an argument about a drug debt.

Thomas C. Muscara had been charged with manslaughter and first-degree assault in the death of Johnny Walton Jr., 51, on March 24.

However, under a plea agreement in which Muscara admitted to stabbing Walton, the manslaughter charge was dropped, and he was convicted of first-degree assault.

He will be sentenced Nov. 29 by Circuit Judge Karen Ahn.

Police initially charged Muscara with second-degree murder, but an Oahu grand jury reduced the charges to assault and manslaughter.

Prosecutors had said Muscara started an argument about a drug debt with Walton at the Makaha condominium complex.

Michael Green, Muscara’s attorney, said during yesterday’s court hearing that after Walton pulled out a knife, Muscara pulled out his own knife and stabbed Walton in the right arm.

The Honolulu Medical Examiner had said Walton bled to death from a stab wound that severed blood vessels in his arm.

Police said Muscara admitted stabbing Walton but claimed it was self-defense. He told police that Walton swung at him with the knife about five times.