An emblem worn by certain Wille members.
Wille （ヴィレ; Ger. "will") is an anti-Nerv organization, dedicated to preventing future Impact events. Its first appearance is in Evangelion 3.0: You Can (Not) Redo.
Wille was formed following the government disbanding of Nerv after Third Impact and comprised of many former Nerv staff members. It is led by Captain Misato Katsuragi. All staff but Misato and the Eva pilots wear a blue bandanna somewhere on their person, usually tied around the upper left arm.
Its operations have been based in an ocean fleet, led by the massive flagship AAA Wunder. After Evangelion Unit-01 is recovered from space and employed as a power source, the fleet becomes airborne.