Mystery Skulls

Shiromori (白森, meaning "White Forest") is a character featured in the "Freaking Out" music video. She appears as a bonsai-like yokai who hunts Mystery to drink his blood. While she initially appears harmless, it is later revealed that she can be ruthless and even sadistic in her quest to find Mystery and will stop at nothing to kill anyone who stands in her way. Shiromori typically adopts a confident expression either after a victory or during a fight. For example, when she first meets Lewis, she has a paralyzed expression, but after recovering from his punch, she quickly regains her confidence.

She's obsessed with Mystery's blood. In "Hellbent," there are several flashbacks, including one showing Mystery tending to a flower or enjoying its presence, followed by another flashback showing him being injured and his blood dripping onto the same flower. The flower's appearance suggests it was Shiromori, before some sort of awakening caused by Mystery's blood. In "The Future," she intended to kill Vivi, but after Mystery, in his kitsune form, bit his paw, causing the bleeding, she was immediately distracted by Mystery. Shiromori has blue skin, shoulder-length white hair, pink eyes, a single sharp fang on the left side, an orange tongue, pink lipstick on her lower lip, pink eyeshadow, feetless legs, rather large hands wrapped in bandages, and a small blue and white tree on her head—similar to a bonsai tree with pink flowers growing from her scalp. In the episode "The Future," she has pink nails that resemble claws.

She wears a traditional Japanese-style robe in white, grayish-pink, and a large pink beaded necklace and bracelets in the same color.
Enemies
Mystery
Vivi
Lewis
??? (Reverb) (possibly)
Target
Find Mystery (successful)
Drink Mystery's blood (failed)

However, a flashback to ancient Japan reveals that things weren't always this way. In "Hellbent," Mystery is shown sitting atop a tree littered with the remains of samurai armor, giggling at Mushi when she encounters him. These flashbacks portray Mystery in a dark, ominous light, implying that in his distant past, he may have been far more malevolent.
Family
Vivi Yukino
Mrs. Yukino
Mr. Yukino
Mushi
Shiromori (possibly earlier)

Mystery is a member of the Mystery Skulls and the team's animal mascot. Mystery is Vivi's beloved dog, but she's unaware that he harbors a dark secret. Mystery's disguise is a white dog with black paws. He has red eyes and a spiky red-and-black mane. He wears tiny glasses with gold lenses and a dog collar with a question mark on it.

His true form is that of a large kitsune with six tails in the episode "Ghost." As of "Freaking Out," he now has seven tails. The reason for this change is unknown; however, one theory is that since he is a kitsune, and kitsune gain a tail every 100 years, he may have simply aged between those two events. In the fourth episode, Mystery assumes his kitsune form and gains two more tails over the course of the video.

After Shiromori's death, he transforms into a black, demonic kitsune with green paws and flames emanating from his back. He has nine tails, each with a yellow eye and a stripe descending to a white tip, and, with the exception of the rightmost white tail, black fur with green accents. From left to right, each tail's stripe represents a color from the rainbow spectrum, and is also white and black. His mouth is a jagged grin with green gums and sharp teeth, his left and right ears are red and green, respectively, and he has three eyes—the left and right have red sclera and white irises, while the middle one is a sickly green with a double yellow-red iris. His glasses are also jagged, and his collar medallion, in addition to a question mark, also features an exclamation point. Little is known about Mister, though he has shown himself to be very loyal and protective of his friends. He can be greedy or have a big appetite, as seen in "Ghost" where he and Vivi empty the fridge and make big sandwiches.

He wears two wristbands, a baggy white T-shirt, and an orange sleeveless vest with three badges: a gold star, a small blue button, and the logo of their team, "Mystery Skulls." He also wears baggy yellow pants and brown high-top sneakers.
Family
Uncle Lance
Mrs. Kingsman (mother)
Mr. Kingsman (father)
Target
Find Lewis (successful)
Enemies
Lewis (former, unknowingly)
??? (Reverb)

Arthur is a member of the Mystery Skulls and a mechanic at his uncle Lance's repair shop, Kingsman Mechanics. Much of Arthur's personality is based on Ben's words and his interactions in music videos.

It's easy to assume Arthur exhibits stubbornness when it comes to those closest to him. As seen in the "Freaking Out" music video, he's sleep-deprived due to his quest to find Lewis, working tirelessly to find him. He's been sleep-deprived to the point of developing bags under his eyes. His loyalty and devotion to his friends is also evident when he and Vivi escape the mansion in a van before Lewis's explosive outburst could injure or kill them. He may have a form of stress disorder due to Mystery ripping off his arm, as he appears to have flashbacks of it and reacts panickily to Mystery's presence.

Arthur is also often considered the most fearful of the group. His official profile (shown on the right) states that he is a "reluctant" paranormal investigator, implying that he may not be as passionate about investigating various phenomena as his friends. In "Ghost," he seems to be the only one frightened by the cave the group enters. Arthur is of approximately average height, with a slim build and broader shoulders. He has pale skin and yellow hair slicked back with two strands of brown hair growing from his hairline upward, one longer than the other.

He has a small, triangular brown beard and sideburns, accented by two orange stripes. His eyes are the same orange hue as the accent lines, and he has two thick, heart-shaped brown eyebrows.

His physiology is typical of a human of his size, with the exception of his left arm, which Mystery bit off after being possessed by Reverb in the cave. In place of his organic limb, he constructed a mechanical arm that functions just like a real one.

Vivi Yukino (雪乃ビビ) is the leader and only female member of the Mystery Skulls team. She is also Lewis's former lover. Vivi is very passionate about the paranormal investigations she and her friends conduct. She is bold and courageous, as the haunted mansion brings her joy, and she throws herself between Arthur and Lewis, willing to take a blow to protect her friend. She cares deeply for her friends and is concerned for the well-being of others, as shown by her refusal to allow Chloe to participate in investigations due to her age. Vivi is slightly shorter than Arthur and has a petite build with very fair skin. She has light blue hair with bangs on the sides and back, falling past her shoulders and held in place by a dark blue headband.

She usually wears a long scarf and a blue down sweater with a short skirt. She wears Mary Janes with short heels and thigh-high stockings. Everything she wears is in lighter/darker shades of blue/blue.

Vivi's entire appearance is blue, except for the lenses of her glasses, which are a striking shade of purple. This is likely a nod to her amnesia following the incident in the cave, although this has not yet been confirmed.
Family
Mrs. Yukino (mother)
Mr. Yukino (father)
Yukino's grandmother (paternal side)
Mushi (possibly a paternal ancestor)
Enemies
Shiromori

Lewis Pepper is a skeletal ghost who haunts the mansion and a former member of the Mystery Skulls. Personality
Lewis was described as a kind person in person. He was deeply in love with Vivi, and they had a strong romantic relationship. He was supportive and devoted to his friends, and was also a loving son and older brother in his family. He possessed intuition and insight, a keen eye, and a quick mind.

After his death, Lewis's grief over Arthur's betrayal shattered him. His love for his best friend turned to hatred and a thirst for revenge that consumed all rational considerations. But despite everything, his heart belonged to Vivi. The brief moment of reconciliation between him and Arthur demonstrates his astonishing capacity for forgiveness.

Lewis enjoys adventure and romance novels and is also a big fan of Sailor Moon and Grim Fandango.
Lewis is a tall, muscular young man with a pompadour hairstyle.

Until death
Lewis had purple hair and slightly tanned skin, and his features were sharp. He wore a purple vest, a white shirt with a purple ascot, dark purple jeans, and purple sneakers.

After death (as a ghost)
Lewis has fiery purple hair, a jawless skull that floats in place, and three ribs protruding from either side of his chest. His hands resemble the gloves worn by the electronic music duo Daft Punk. He wears a black suit with bat-wing lapels and a white shirt with a purple-pink tie. Near his left chest is his heart medallion, which is gold (sometimes blue or gray).
Family
Mrs. Pepper (foster mother)
Mr. Pepper (adoptive father)
Paprika (foster sister)
Cayenne (foster sister)
Belle (adopted sister)
Target
Take revenge on Arthur
Return to Vivi
Enemies
Arthur Kingsman (formerly)
Shiromori
??? (Reverb)

Reverb is a green creature that possessed Arthur's left arm and used it to kill Lewis Pepper. He serves as the main antagonist in the episodes. Reverb's origins are unknown, but he lived in an abandoned cave outside of town. In a flashback from the episode "Ghost," while the Mystery Skulls were exploring the cave one night, Reverb possessed Arthur and slowly took over the left half of his body. He then forced Arthur to push Lewis off a cliff to his death. However, before Arthur could fully become possessed, Mystery chewed Arthur's arm off his body, leaving Reverb without a host. Little is known about Reverb's personality, other than the fact that he seems to be indiscriminately aggressive and malicious.

He is the most evil creature known to humans and youkai, far surpassing even Shiromori in hostility.

From the events of the episode "The Future," it can be concluded that Reverb is very patient and manipulative, quietly watching the team and waiting for the right moment to take possession of Mystery. His enemies include the Mystyre Skulls team and Shiromori (possibly).