Vassal Mirror

The Vassal Mirror is one of the Eight Vassal Weapons from Glass' World. The person who possesses the weapon is called the Mirror Hero. The current wielder of the mirror is Naofumi Iwatani.

Overview
The first known user of the Vassal Mirror is Albert, who was a reincarnated individual being manipulated by Kyo. His country, Mikakage, was the one that housed the entrance to the Infinite Labyrinth where Kizuna was trapped. Albert was later killed by Kyo and used as one of his experiments with the Vassal Mirror chained to his corpse. During the raid on Kyo's compound, Naofumi eventually liberated the Vassal Mirror which then helped him defeat Kyo. After the battle, the Vassal Mirror flew away with the newly liberated Vassal Book.

When Kizuna was kidnapped trying to reunite her world, the Vassal Mirror used its transportation abilities to move the heroes to near her location. During the heroes' mission to rescue the kidnapped Kizuna from Miyaji, Naofumi and Itsuki's Legendary Weapons were suppressed and they were almost killed. However, the Vassal Mirror and the Vassal Book appeared just in time to save the heroes. Both weapons tried to make Naofumi their user but only the Vassal Mirror was successful. With their help, Miyaji and his companions were defeated and Naofumi remained the Vassal Mirror wielder.

The Vassal Mirror works similarly to the Legendary Shield, except it specializes it defending and reflecting magical attacks. It also has a wide range of transportation abilities.

Power-up Method
The power-up method for the Vassal Mirror is "food level." This power-up ability increases a food level gauge that is different from regular levels. Levelling up causes statuses to increase. Different food changes which statuses are increased. Unlike many power-up abilities, this can affect both heroes and non-heroes.

Trivia

 * In the Web Novel, Kuu wielded the Vassal Mirror.
 * Apparently the former Mirror Hero Albert did not use the food level power-up method since he didn't want his harem to be fat.