So, Ayaka and Sigma are two characters split from the concept of Fake/states Night's multi-Servanted protagonist. This idea expresses itself in Richard's seven retinue and Watcher's seven shades. Richard's friends are explicitly said to follow the framework of the seven regular classes, but since Watcher's shades are also seven, I wonder if they're meant to fit the same frames. I think it can work like
Saber Stephen
Archer Orion
Lancer Ahab (harpoon)
Rider Amelia Earhart
Caster Asclepius
Assassin Musashi
Berserker Icarus