9'ζ, η, θ

9'ζ (Nine Zeta): She is a female pistil (pistil role) in the elite Nines squad, serving as the partner of the squad leader 9'α (Nine Alpha). She is one of three identical triplet-like pistils (along with η and θ), characterized by white hair, grey eyes, and wearing a silver mask. She has very little screen time or dialogue and dies later in the story due to lack of maintenance after a major battle.

9'η (Nine Eta): She is another female pistil in the Nines, partnered with 9'β (Nine Beta). Like Zeta and Theta, she is visually identical to the other two in the trio — white hair, grey eyes, silver mask — and belongs to the same triplet group. She also has minimal presence in the series and dies in episode 23.

9'θ (Nine Theta): The third female pistil in this set, partnered with 9'γ (Nine Gamma). She shares the exact same appearance as 9'ζ and 9'η (white hair, grey eyes, silver mask) as part of the identical trio. She receives almost no individual focus or lines and meets her end in episode 23.

These three are background members of the Nines (a special forces unit of enhanced parasites), often appearing together silently as a set to fill out the squad. They don't have speaking roles or significant character development in the anime.