Kaguya Ray Peram Westcott

"My true wish? To dismantle this world. Why? For the fun of it. Anger. Sorrow. Despair. Nothing else gives me the same kick. They're my pleasure and joy. I want to watch the residents of some inconsequential world be torn apart... That's all. That's right! This Spirit amalgam's falling apart the seams! Can you believe the information of just one man made me fall from grace?! You may learn from the true nature of his evil and alien madness!"

- Kaguya to the heroes.

"I'm sorry Liliruca. I needed a replacement Spirit twin to make the act convincing! I really am sorry I didn't kill you the way! But rest assured! I'll kill you now, "Yuzuru"...a̶n̵d̶ ̵b̷u̷r̶y̶ ̷y̴o̷u̷ ̶i̷n̸ ̶c̵o̶l̶d̸-̷b̸l̴o̴o̵d̴!̵"

- Kaguya to Lilirica.

Kaguya Yamai, later revealed to be Isaac Ray Peram Westcott, and later known as Kaguya "Westcott" is the main antagonist of the 2019 crossover game Danmachi X Date A Live Collaboration - Ais Catastrophe. Kaguya was a fragmental Spirit born from the mana of all Spirits sealed by hero Shido Itsuka and the mastermind who teleported the heroes of Date A Live universe to Damanchi world. She was later revealed to be a Spirit Amalgam merged with Westcott's personality, becoming a new Isaac Westcott from the Second World. She serves as the evil counterpart of Mayuri.

She was a immensely powerful Spirit who could use the power of all Angels from the Sephira Tree and could easily manipulate the powers of the Spirit of Origin, Mio Takamiya, to turn other being in Spirits as easily as Mio could. Her ultimate goal was the destruction of the multiverse and by a far extension, the only antagonist of both franchises to be a multiversal threat with octillions of victims.

She was voiced by her original VA, Maaya Uchida, who also voices Kaguya's twin sister, Yuzuru Yamai.

Appearance
Despite being different entities, Kaguya was similar to her original counterpart.

Her hair is braided up, and she has a lean figure. She has a determined expression for most of the time. Kaguya's Astral Dress is mainly the color purple and has chains on her right hand and foot. The lower half of her body has a half skirt around her waist which drops to the knees and opens around her thighs. On her insane form, she have red empty eyes, just like Isaac Westcott's dead blue eyes.

Kaguya's height is stated to be 157cm, and her three sizes are B79/W56/H81.

Personality
"Westcott" was good (almost perfect) in imitating the original Kaguya. She was outgoing and outspoken to the point of being childish or immature. Unlike Yuzuru, she reacted violently to critiscism and refused to let others tell her what to do.

Kaguya often speaks rather unrealistically, as if she is acting. It is later revealed that it really is acting. Kaguya believes she needs to talk like this because she is a Spirit, and therefore "super awesome", and therefore must act appropriately.

After she shows her true clolors, she showed to be a twisted and insane Spirit. She sees everything existing for her sake and inflicts betrayal purely because she loves the expression on her victim's face when their friends and family are turned against them. When Liliruca asked why she deceived her for so long, she immediately starts acting like she's the victim and feels sorry for not killing her before exposing herself to be the mastermind behind all the tragedies of the heroes' party.

Kaguya was a Spirit with complete and utter obsession with war, genocide, despair and destruction, and even stating she sees the multiverse as her plaything to travel and destroy worlds with her heart's content. She loves sorrow in any and all of its aspects; even if she is the one suffering or having her own life at risk provokes nothing but glee and excitement.

Background
Kaguya was born as a pure spirit born from the mana of all Spirits sealed by Shido Itsuka in his world. During her time alive, she was born as an innocent Spirit but in the meantime she admired the corrupt director of Deus.Ex.Machina Industries, Isaac Westcott, and all of his atrocities and ambition. By her own free will, she decided merge herself with Westcott's persona, copying him and consequently becoming HIM in the body of a Spirit.

After becoming Westcott, now reborn as Kaguya, discovered the existence of other multiverses using the power she stole from other Spirits and decided to set herself as the rule of all existence by destroying the entire multiverse and killing all Gods of the existence. To start her own plans, she begins merging two worlds at the same time together. These "mergings" lead to catastrophic damage across both of the merging worlds, while also creating phenomenon that summon monsters in both worlds. These alone lead to the deaths of thousands of innocents on various worlds.

Current events
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Natsumi's Arsenal
Unlike the other Spirits, Kaguya possesses not just one but all Angels of all Spirits who showed up on Earth. Her mostly notable ability was the power she stole from Natsumi. Kaguya has the power of transformation and shape-shifting, being able to turn anything into anything else within a range of 1 kilometer, including herself. If she loses concentration or becomes unconscious, all that had been transformed will return to their original state.

The transformed objects or subjects, including herself if she transforms, will be a near-perfect imitation of whatever they were transformed into. However, the memories and personalities of the transformed objects or subjects will remain the same.

Kurumi Tokisaki's Arsenal
Like Kurumi, Kaguya has the ability to manipulate mainly time, but her main power is associated with controlling shadows. Shadow is her primary element while Time is her secondary element in terms of usage. Combined with the power of the 8th bullet, she can create a clone that has all her experiences, memories, abilities, etc.

These clones can take the form of long white hands with red outlining when they are in Kurumi/Kaguya's shadows. However, as these are her past selves, they sometimes may contain feelings which the current Kurumi/Kaguya no longer possesses and as such, Kurumi/Kaguya will not hesitate to kill these clones if they choose to disobey her. These clones are less powerful than Kurumi/Kaguya herself as she has mentioned in the last chapter of Volume 3 and in the epilogue of Volume 4. She can form a single clone by shooting herself with Zafkiel's 8th bullet, or bring out all of her clones at once from the shadows which she keeps them in. She can also use these shadows to store her clones all at once and all the time they've collected, if she needs to do so. She can also control her clones partially through small fields of shadows, most often to hold someone in place and prevent them from moving.

Yamai's Arsenal
Like the Yamai Sisters (mainly Kaguya), she have the power of the original; have the power to manipulate wind. They can gracefully control the air currents in order to glide through the sky. At their full power, both of them can easily create a typhoon that can blow away a small island.

Trivia

 * Kaguya in this world is probably the most evil and insane version of any Spirit to show up so far in the entire franchise, even more so Kurumi Tokisaki who was utterly disgusted of her atrocities and crimes.
 * This is not the first twisted version of Kaguya to exist in the series. The first "evil" version of Kaguya appeared alongside her sister, Yuzuru, in a fantasy comedy side-story where they are the generals of the Demon King who was sealed in a distant land but were set free after a thousand years. In this version, they represent the typical fantasy demons (notable for being Succubus) trying to seduce the hero (Shido Itsuka) into tricking him to let their leader, the Demon King, to kidnap the princess (Tohka Yatogami) and marry her against her will. However, unlike the demonic version of Yamai, this version of Kaguya reborn as Westcott is the most serious, dark and evil version of Yamai to date so far.
 * Yamai Westcott was reborn with empty eyes like if she was brainwashed or suffering, however, it was revealed they were the eyes of Isaac Westcott, that are known for being empty dark-blue eyes. The fact they are red means she is even more insane than the original Westcott from the Prime Earth.
 * This is not the first time that an original Spirit is born from the mana of all Spirits in the franchise. The first Spirit to be born from pure mana was Mayuri, the first Spirit to be born from the mana that Tohka, Yoshino, Kotori, Kaguya, Yuzuru, and Miku unconsciously emitted due to their stress and desire to have Shido all to themselves. However, since she was born from spirit mana, she would eventually disappear. Unlike Mayuri, Kaguya had no problem in living with the existence of other Spirits.