| Character Information
Vulcan (ウルカヌス Urukanusu) is the eldest of the Jupiter Sisters and Tsukiyo Kujyō is her host. She is the third goddess to be revealed.
When Vulcan is in control of Tsukiyo's body, Tsukiyo's hair and eyes acquire a crimson-red color. Like the other goddesses, Vulcan also has a halo and a pair of wings behind her back.
Despite her disabilities — feeble eyesight and poor hearing — Vulcan is very powerful. According to her, she breathes souls into inanimate objects so that they can act as her eyes, ears, hands, etc. She also reveals that she is able to use telekinesis, considering what she does to the objects in the library in order to attack Keima. Vulcan can only control inorganic objects, however, and seeing as she is unable to walk, she uses Luna as her "body".
Contrary to her inability to walk, Vulcan is still able to fly without difficulty.
Vulcan is a goddess who loves justice and delicacy. As such, she is willing to do anything to protect Tsukiyo, who she considers to be the embodiment of elegance.
Vulcan is a very charming lady. Towards the people she is fond of, like her sisters and Tsukiyo, she tends to speak with proper etiquette. She is fiercely protective of Tsukiyo, and sees Tsukiyo as a beautiful and pure girl. Conversely, she displays a rather aggressive behavior towards Keima and will not hesitate to punish him should he do anything that displeases Tsukiyo.
Additionally, because of Keima's disloyalty towards his conquest targets, his very being disgusts Vulcan. However, Vulcan has grudgingly accepted that Keima is desired by Tsukiyo, so she decides to aid Tsukiyo by telling (threatening) him that he should only be with Tsukiyo and no others.
In an omake, during some time spent with Tsukiyo, Vulcan shows that she becomes irritated when she is treated as an elder due to her poor eyesight and hearing.
Vulcan and her sisters are responsible for the past sealing of Old Hell. Their heroics unfortunately trapped them along with the Spirits, but were released when the seal is broken. At some point after the event, Vulcan enters Tsukiyo Kujyō, presumably along with Tsukiyo's runaway spirit. However, unlike the spirit, Vulcan had no immediate effect on Tsukiyo.
During the hunt for the goddesses, Vulcan begins to regain her powers through reasons related to Kanon's love confession. Vulcan displays some of her power by controlling Tsukiyo's doll, Luna. Being someone who strongly believes in justice, she decides to use Luna to punish Keima after seeing him with Shiori and for being unfaithful to Tsukiyo.
No actual relation except for the fact that Vulcan uses Luna as an extension of her senses. Tsukiyo originally believed that Vulcan was Luna brought to life.
With their mutual acceptance of Keima being a disgusting man, Vulcan and Tsukiyo form a meaningful friendship. Tsukiyo is Vulcan's good friend, and Vulcan wishes for Tsukiyo's happiness because of Tsukiyo's beauty and delicateness. The two treat each other with the utmost respect, as evidenced by their conversations.
Disgusted at the fact that Keima is involved with numerous relationships, Vulcan's primary feeling concerning Keima is something similar to utter disgust. Her loathing towards Keima is strong enough that she is willing to do almost anything to protect Tsukiyo from him. However, after Tsukiyo admits that she still has romantic feelings for Keima, Vulcan reluctantly decides to aid Tsukiyo in acquiring Keima's attention.
Being the eldest of the Jupiter sisters, Vulcan is highly admired by her younger siblings. Also, since she is the eldest, she tends to have a very slight commanding tone when addressing her sisters, though the tone is mostly ignored by her siblings aside from Diana and Minerva. Despite this, Vulcan makes sure to treat her sisters with respect.