フィラメント

One of Saki's personas. This persona undertakes all of the pain Saki can't withstand.
These multiple personae come into existence when someone forcefully segregates her traumatic feelings in order to defend her psyche. Filament is a paragon of such a persona.
Because of her background, she knows things about Saki that Saki herself doesn't even know.
Her knowledge often helps the party.