Answer
The "Kenzo Tenma" portrayal in the anime series Monster belongs to Liam O'Brien, an accomplished actor in voice-over work. O'Brien brings his talent and experience to life in giving voice to Kenzo Tenma, a pivotal character within the series. This character portrayal is just one of many that highlights O'Brien's versatility and skill in the field of voice acting, making him a standout performer in the industry.