Light Yagami's actions in the series "Death Note" significantly contribute to the narrative tension and suspense. His manipulation of the Death Note to eliminate criminals and establish a new world order builds suspense as viewers wonder if he will succeed in his plans or if he will be stopped. The moral ambiguity of his actions adds complexity to the storyline, keeping the audience engaged and questioning the consequences of his choices. Overall, Light Yagami's actions create a compelling and intense narrative that keeps viewers on the edge of their seats.