Its 24 episodes center on high schooler Shinichi Izumi's forced symbiosis with the parasite Migi after a failed brain invasion, leading to battles against other parasites that devour humans (Ep 1-2, 6-7, 10, 20-23). Core conflicts involve survival, loss (Shinichi's mother in Ep 6), moral questions about humanity versus instinct, and coexistence, drawn directly from the source material's environmental philosophy and anthropocentrism critique.

Creator Iwaaki explicitly aimed to explore human egotism over the planet from an ordinary viewpoint without condescension. No episodes feature identity politics, systemic oppression narratives, DEI-driven casting, LGBTQ+ normalization, or critiques of traditional norms.

Voice casting pairs Nobunaga Shimazaki as Shinichi and Aya Hirano as Migi with no established-character alterations or cross-sex live-action issues. Reception highlights its horror-action storytelling and philosophical depth without modern activist overlays.