(Summary) White Cosmos - Black Lotus - Red Rider

The white king is her one year older sister and her Parent. She doesn't possess any natural attack power, and she doesn't appear in front of anybody besides her legions top lieutenants. KYH mentions she used to fight in the very beginning of Brain Burst (implying she is an originator), but that she used something, either an ability or a enhanced armament, that made he enveloped with light so the opponent couldn't see her form (essentially confirming she is the person with Black Vise in the Chrome disaster back-story).

The White king approached KYH and showed her a gun made by Red Rider, claiming that one of it would be given to every legion, would only be usable when your legion is attacked, and never missed, had infinite ammo and devastating power. She made a demonstration of the power of the gun, and said it was to be a deterrent that would make it impossible to attack another legion, as the defending side would always win, essentially enforcing the truce regardless of the other kings opinions.
KYH kills him with the intention of stopping the making of the other guns. However, after the destruction of NN, while she was already in hiding, she notices that, when she killed Rider, one of the guns was transferred to her inventory, as sometimes happens when you kill someone. The weapon in unlocked, but it won't fire. She realized he made it that way as a symbol of peace. She runs to her sister's room to accuse her, to which she only agrees to everything, smiling. Hime tried to force her into a duel with a box cutter, but her sister tells her not to do that, as she doesn't want to take even brain burst away from her. Hime, realizing she could never win, ends up stabbing her in the hand, and that's how she was thrown out of the house.