She was born with heart failure and usually stays in hospital. Because of her wish for "not want to die", She was transformed by Sanpikime - one of the Original Three - to a mushitauki. Her bug is a silver Morpho butterfly that can fuse on objects and releasing butterfly wing powder that can cause devastating damage or used as a defensive shield to blow away attacks. This also gives her super strength despite of her handicaps. Her bug also consumes dreams from the others instead of her's. At times she would go out and search for the "Undead Mishitsuki" to find out the way not to die, she also attacks various Mushitsuki during the process so this gives her the alternative name "Hunter". She is also appointed rank 1 by SEPB because she had killed many bugs owned by high rank members of the SEPB. Sanpikime praised her as "the strongest Mushitsuki ever existed." At the beginning of the series, she was already passed away. But her bug was still alive and was transferred to Arisu, her sole friend. She relives the story from her favorite picture book and was given the option to choose between "Angel's Elixir" (She would live but being remembered by no one) and "Devil's Elixir" (She would die but being remembered by all). At first, she choices "Angel's Elixir" and transferred her conscious and personality to her bug. She can show her personality by taken over Arisu's body, and will eventually replace Arisu if she wishes. Her plan was almost successful, but she changed her mind at the last moment and decided to leave her hope to Arisu, and chooses the "Devil's Elixir" to die. She is voiced by Ami Koshimizu in the Drama CD adaptation.
Erii is a young Mushitsuki who controls a pack of White Swallowtail butterflies to manipulate electrics. She can gain access to all equipment that requires electrics to operate, and can even have visions by sending currents through any medium that conducts electrics. These proven to be very powerful abilities in the urban environment. She can also summon her White Swallowtail butterfly to shoot electric beams to paralyze opponents. Her dream is to "know every secrets about the world." In Mushi-uta Bug Vol. 5, ch.18, She was discovered by Central SEPB, and Daisuke brought Arisu and Neiko to investigate. Arisu used her ability to "challenge" Daisuke and his company but Daisuke managed to break every obstacles. When she was discovered, her brain was about to burnout by uncontrollably accessing too much information, but she was too afraid to shut down her power. Daisuke did an unusual act, which was to spare her, and convinced her to shut down power with Arisu. Erii was later sent to Eastern Central SEPB under the supervisor of Inuko. She slowly learned how to control her power and became a high ranked member in the intelligence section of Central SEPB. Erii also made an appearance in the anime adaptation: She was sent with Kasuou and Kirikiri to investigate Azami's power. She was left outside when Kasuou and Kirikiri got sucked into Azami's handycam. She also helped Daisuke to get into the handycam and saved him from it. Erii holds a complicated love and admiration toward Daisuke, she also thinks that Daisuke and Arisu have the ability to fix the distorted world full of Mushitsuki. She lost half of her hope when Arisu sacrificed herself in the battle of "meteor night," so she put all her remaining hope on Daisuke and gradually became heavily depend on him. She showed an unusual anger to Daisuke when he decided to "betray" SEPB in Vol.3 and "reject" her. She also executed a failed assassination targeting Shiika because she thinks Shiika would "drag Daisuke away from his goal." Deep in her heart, Erii never wished to stop the war between Mushitsuki. Yaeko used her thought to convince her to become a test subject by implanting Shinbu's body fragments which will grant her power to gain "many friends." Erii hated herself and felt she was betraying Daisuke, Arisu and all the Mushitsuki who battles hard to end the war. She wish Daisuke can stop and kill her. She gradually lost her personality and couldn't distinguish herself from Shinbu, the new creation of the mixture became the foundation of "C." In vol.13, in order to escape C, Erii excluded her personality and transmitted it as digital information to a disposed satellite debris on earth orbit. To prove she have bravely fought to end the unending Mushitsuki civil war, so she could face Daisuke and Arisu with no shame, she planned to control the debris to strike earth to kill "Alpha," which will produce new Mushitsuki endlessly. Shiika and Neo-Mushibane tried to stop the debris and take her memories back. However, such plan was used by C trying to absorb the last bit of Erii to become even more stronger. Shiika risked her life to save Erii being absorbed, but was unable to save Erii's memory device. Erii changed the course at the last moment, with the help of Sanbikimei in Chiharu, left everyone no harm when impacted. Erii left her dying message to everyone: "please protect Yuu (from being taken by Oogui)."
He is the leader of "Harukiyo Clan" and a Mushitsuki who processed the power that rivals or even suppress that of Daisuke's. His bug is a giant Tiger Beetle that produces high temperature flames intense enough to burn or melt anything. He is allied with Miguruma Yaeko, the vice-presedent of Central SEPB branch. He is only interested in battling with strong opponents. Although usually described as savage, cruel and heartless, he actually cares a lot of his "friends". He seems to be targeting something hidden deep inside Central SEPB's underground facility. He wishes to be punished by the strong, so in Mushi-uta Bug he was looking for Mari as he felt that Mari is strong enough to punish him. He felt very depressed about Mari's death. He later traced down Mari's Morpho Butterfly and started to follow Arisu. Although he did not recognize Arisu's strength, he did reveal his dreams to her and promised to watch over Morpho Butterfly to the end. He also joined the last battle of "Meteor Night." He is the one who responsible for burning down Aoharima Island while battling Sanpikime, but he did not kill the residents on it. He is finally able to approach his target - Arisu, at the end of Volume 12, but as soon as he awakens Arisu, he is immediately defeated. Before the final battle, his mind was polluted by C's psychological attack and sees the illusive version of people who died because of him. This caused him to fall into despair. Sanpikime injected the memories of Daisuke into his mind and saved his heart through a illusive battle with Kakkou. Harukiyo was able to stand again and stop Daisuke's bug from turning into mature state. He was very active in the final battle. He was last seen targeting Yaeko, who appeared in front of Chami. Whether he succeeded in doing so or not remained unanswered. Which organization he currently affiliated with is also not answered. He is voiced by Takahiro Sakurai in Drama CD adaptation.
Suku is the boy with the red cape and metal ring around him with a Kanji character. He is a member of Noshiga's gang and seems to be the second in command next to Noshiga. However once the demons make their entrance his tough front vanishes and he runs away right before Noshiga pushes Tachiji in the way of the Kimo-Tori (Liver-Taker) demon. After Noshiga yells at him to get lost and find a different place to hide his is captured by a demon. He is taken by the Kimo-Tori (Liver-Taker) demon and shortly after his gang leader, Noshiga is captured by the Chi-Tori (Blood-Taker) demon.