Beni

"With this rouge, I become Beniyasha, Destroyer of Lands. Tremble before the bloodthirsty dawn! Bear witness to your end, if you dare!"

- Moroha using her Beni

The is a cosmetic product used to apply color to the lips. The quarter-demon Moroha can temporarily transform into Beniyasha by using her rouge which also gives her the memories of her late dog-demon grandfather. Decades ago, it was originally given to Kikyō as a gift by Inuyasha, but was later destroyed by the shapeshifting demon Naraku when he had posed as Inuyasha, in order to kill Kikyō.

Riku had somehow managed to reconstruct it and presented it to Hōsenki II, for the Black Pearl to be made again for Inuyasha, who scornfully rejected them both with the claim that he could do whatever he wanted with his human mother's keepsakes.

History
In the anime, Izayoi is shown to have been born in a wealthy/noble family and possibly used the rouge to present herself on formal occasions. After her death Inuyasha kept his mother's rouge as a memento, along with the Robe of the Fire-Rat. Some time later, Inuyasha would gave the rouge to his first love Kikyō as a gift. The rouge was later crushed by Naraku when he struck her down.

Inuyasha's and Kagome's only daughter Moroha currently holds a rouge that gives her the ability to transform into Beniyasha. According to Myōga this rouge was given to Izayoi by Tōga and have a unique property. Moroha also stores the Red Rainbow Pearl she obtained from Tōkotsu inside her rouge compact.

When Moroha was trapped in a dream during the fight with Yotsume, it is shown that Kagome had to tearfully pass Izayoi's rouge as a parting gift to her infant daughter in an unknown incident involving herself, Inuyasha, Sesshōmaru and Kirinmaru.

It was later revealed that after Naraku destroyed the original rouge, it's fragments were gathered and made into a new one, which contain Izayoi's tears of grief for her husband's death, so that Riku had the Yōkai jeweler Hōsenki II use it to create the Black Pearl, the later which can create a path to Tōga's tomb.

Physical description
The rouge appears as a red thick cosmetic cream stored inside a scallop shell compact that has a tiny red bow tie decoration at its beak. Moroha's Red Rainbow Pearl can be seen inside her shell compact until it was scattered throughout the lands by Kirinmaru in the first season finale.

Demonic Properties and Skills

 * Demonic Transformation: When Moroha applies it, Myōga had stated that "Tōga's memories are revived in her blood", and she becomes Beniyasha, therefore gaining access to her own dog-demon form as her father had in dire situations. Its full strength is yet to be unleashed. This temporary evolved demonic form is known as "Beniyasha" which could mean "demon spirit of the rouge."
 * Skeleton Melting: Beniyasha emits an aura that is strong enough to disintegrate bones like Jakotsumaru's red skeleton guards (except for his father).
 * Demonic Ability/Power Augmentation: The demon blood of Tōga amplifies his youngest granddaughter's natural abilities to greater levels but only for a few moments. It increases her natural superhuman strength, agility, speed, durability, and reflexes, and makes her fangs and claws ten times sharper than normal; a feat that Kirinmaru admires. At one point, her Crimson Dragon Wave technique had been magnified to the point that became somewhat larger and brighter, and strong enough to obey to Moroha's strong will alone. However, this advancement could only have happened due to Tōga's powerful essence aiding her and not from her evolved Beniyasha form.
 * Demonic Energy/Essence Projection: At one point, her blood-red demonic aura takes on the fiery orange form of her late grandfather's humanoid form, further magnifying her enhanced senses and her sword's Crimson Dragon attacks twenty times greater. It could have been Moroha's vortex of enhanced demonic energies combined with that of Tōga's essence that resided within the soil.

Trivia

 * It is customary since ancient times for women (at first for noble women, later for common women as well) to use cosmetics, including lip-coloring makeup.
 * In "Kagome's Instinctive Choice," its final appearance in InuYasha is seen in a memory-dream by Kagome as she is attempting to heal a fatally hurt Kikyo from Naraku's miasma.
 * Kirinmaru expresses his respect for Moroha's natural dog-demon abilities and strength when they are increased somewhat from her applying the pure demon blood of her late paternal grandfather, but is amused that she is incapable of maintaining such a powerful and deadly demonic form for longer than a few moments.
 * It is in the title of Episode Nineteen of Hanyō no Yashahime, but it is never seen or used by Moroha.
 * Kirinmaru is impressed and intrigued at it granting Moroha greater demonic strength from the late Tōga's blood and memories.
 * It had put Moroha on the same power-level as Setsuna, whose demonic side was just released due to Zero's intervention, but then Setsuna had overpowered her in nearly ten minutes. Moroha had referred to applying the demon blood to her lips was a way for her to "go all out" against much stronger adversaries.