Osaka Prefectural Gymnasium
In September of the same year, Muguruma was tied on points with Wilfredo Vázquez in the fight for the WBA bantamweight title at the Osaka Prefectural Gymnasium. Muguruma moved back a weight class to fight against Juan José Estrada for the WBA super bantamweight title in Moriguchi in October 1988. However he suffered an eleventh round stoppage with the towel thrown in, after being floored in the fourth and eleventh rounds, and hung up his gloves.