The Marys

Subject: The Marys
Category: surveillance force
Era: Present
Related: Cyborg Den Den Mushi
Name meaning: JP メアリーズ (Mearīzu) = the English plural 'the Marys.' The 'Mary' (メアリー, mearī) is a cross-language pun on 目あり (me ari, 'have eyes'), lifted from the proverb 壁に耳あり障子に目あり (kabe ni mimi ari, shōji ni me ari) — 'walls have ears, sliding doors have eyes', the Japanese equivalent of 'the walls have ears.' Apt for a surveillance force that literally 'has eyes' everywhere on Onigashima; the pun is reinforced visually — each Mary (human or cyborg animal) wears a paper mask with a single eye drawn on it (= me ari).

Structural lore — Kaido’s island-surveillance force on Onigashima, first named and explained on-page Ch. 1005.

What we know

Ch. 1005 (p. 14): “the Marys” are Kaido’s surveillance force on Onigashima. The roaming cyborg/mechanical animals (e.g. a mouse) are not autonomous spies — they share their eyesight with human “Mary” operators, so anything a Mary-animal sees is seen by Kaido’s watchers.
Ch. 1005 (p. 14): the animals “wander around the island without a purpose,” making them easy to overlook — being seen by one means the enemy already knows your location (“So it DID see us!! We’re not safe here!!”).
First on-page identification delivered by Yamato, who names it “my father’s surveillance force” after a cyborg mouse overhears “Sangoro’s” (Sanji’s) broadcast voice near her hidden storeroom.
Name etymology (resolved): メアリーズ (Mearīzu) “the Marys” — the “Mary” (メアリー mearī) puns on 目あり (me ari, “have eyes”) from the proverb 壁に耳あり障子に目あり (“walls have ears, sliding doors have eyes”). The force that “has eyes” everywhere; each Mary’s mask carries a single drawn eye. See etymology in frontmatter (medium confidence; source: One Piece Wiki, Beasts Pirates → Marys).

The Mary-animals are roaming cyborg/mechanical beasts dispersed across the dome; each pairs to a human “Mary” operator who watches through its eyes (an eyesight-sharing relay, conceptually adjacent to the Visual Den Den Mushi). See Cyborg.

How extensive is the Mary network across the dome, and who are the human “Mary” operators?