The "Unlimited Panty".
The Unlimited Panty (アンリミテッドパンツ, Anrimiteddo Pantsu), also known as the Ultimate Butt's Armor (究極の尻鎧, Kyūkyoku no Shiri Yoroi), and Shigeo Net Panty (しげ夫の網パンツ, Shigeotto no Ami Pantsu), is a strengthened, legendary swimsuit, designed to empower its wearer. Its wearer is said to be able to receive a great amount of strength, like a god of war. This swimsuit has been delivered to certain West players. Upon seeing a photograph given by Meiko Ginya, Sumire Sakuragi finds out that Ai Shinonome is the one who delivers them, leading her to be revealed as "Ai Fujisaki", the eldest daughter of the Fujisaki Family. The creator of this swimsuit is revealed to be other than Shigeo Fujisaki. Confronting her mother, Ai asks why does she spread the "Unlimited Panty", which is an illegal and unfair item. Reiko Fujisaki declares that she wants to take down the Five Butts in order to restore the balance between the East and West. Thus, she delivered the item to certain West players who could match the Five Butts.