Lazaro is a supporting character in the anime Cagaster of an Insect Cage, a figure whose past and actions shape much of the story's conflict. He is an adult man with brown eyes and medium-length black hair, often depicted with stubble and wearing a cross, giving him the appearance of a weathered priest or wanderer. Lazaro was originally a soldier and an exterminator, credited as the first person to systematically fight the giant carnivorous insects known as Cagasters. He played a crucial role in preventing the complete collapse of human civilization in the eastern regions. He became the adoptive father and mentor of Kidou, the story's protagonist, teaching him everything he knows about survival and insect extermination. Lazaro's teaching methods were harsh and unsentimental, never coddling Kidou, which instilled in the boy a hardened but capable mindset.

Despite his heroic beginnings, Lazaro developed a deeply nihilistic outlook. He worked for the good of his community but eventually became unfit to lead because of his disagreements with the military authority. His disillusionment grew when he himself was diagnosed with the Cagaster disease. He was betrayed by people he trusted, who saw him as a burden because of his infection. This betrayal turned Lazaro bitter and resentful toward humanity. He transformed into a Cagaster insect, but unlike most infected, he retained his human consciousness. As a result, he began to see himself as a superior being, neither fully human nor fully insect. His motivations shifted from protecting people to seeking a new world order in which he would rule at the top.

In the story, Lazaro initially serves as a background figure whose influence is felt through Kidou's skills and memories. Later, he emerges as a major antagonist, having allied himself with the insects and become their leader. His key relationships include his role as Kidou's foster father, a bond that is both formative and ultimately tragic as the two face each other in conflict. He also has ties to the military and the community he once served, but those connections are severed by his transformation and betrayal.

Throughout the series, Lazaro undergoes significant development from a selfless protector to a bitter, power-hungry adversary. His abilities are formidable: he is a highly skilled fighter and strategist, having survived and fought in the Cagaster-infested Far East for years. After his infection, he gains the physical traits of an insect, including enhanced strength and the ability to command other Cagasters. His retained human intellect makes him a particularly dangerous and calculating enemy. Lazaro's arc serves as a cautionary tale about how a once-heroic figure can be twisted by trauma and betrayal into a threat to the very people he once defended.