|Title||The Portal Demon|
|First Appearance||Alliance of the Golden Witch|
|Voiced By||Yuki Kaida|
Gaap (ガァプ Gaapu ) is a demon with the power of gaps, holes that can reach almost anywhere. She is very fashionable and up-to-date on the latest trends. One of the 72 Great Demons, the 33rd highest ranking earl of the underworld. Also Beatrice's friend.
She was summoned forth by Goldsmith. At the first twilight, she used her power to create gaps in the floor of the parlor, trapping Nanjo, Kyrie, Krauss, Kanon and Shannon into a dungeon in Kuwadorian.
Later on, she was the one who tested George for the inheritance of the Ushiromiya family. She fought against him for some time, and could have been killed several times during the battle, but she outwitted him in the end. She opened a gap when Jessica was about to hit Ronove's shield to block George's attack, killing both Jessica and George instantly.
Through the entire chapter, there is a rivalry between Virgilia and Gaap. She makes fun of Virgilia's name by shortening it to "Lia" but the older witch cannot shorten Gaap's name. Instead, she calls her Gap repeatedly when mad at her.
Gaap helps Beatrice save the illusion of Kinzo. When Kinzo was locked up in his' study and risked to be destroyed by Erika she proposed to stay with him and in case things went bad she could make both of them dissapear with one of her gaps. Beatrice though, hinting the danger of the situation they were in, refused to let Gaap take care of the situation since she could go though serious danger. She assists with Ronove at Battler's salvation of Beatrice and seeing from high the majestic figure she sighs in admiration for Battler. She later assists to the witch trial called by Erika and Bernakstel and calls Beatrice to her senses trying to make her give up the game and spare her life. However Beatrice decides to go for it all so Gaap can do nothing but watch Beatrice die and her illusion disappear.
Gaap, along with all of Beatrice's entourage, helped trying to solve Battler's Logic error issue and get Beatrice at the wedding for her final showdown with Erika. When Beatrice won the love trial against Erika she hugged her with joy as Virgilia, Ronove and the Seven Purgatory Sisters.
Gaap is a revealed to be mere illusion of Yasu's, created to justify with magic the incidents that occured whenever Yasu was distracted during job. Representing the playful nature of the Golden Witch Beatrice, from a magical point of view Gaap loves to play pranks on all the servants, especially on Yasu who is an atypical person.
First shown teasing Yasu over a cleaning tool in the Chapel, Gaap's presence is detected by Yasu, who begs for Gaap to return the small broom Yasu had been using to clean. After that day Yasu and Gaap become friends, even though Gaap still pulled pranks on her new friend. When Yasu becomes responsible thanks to the "charms" Kumasawa gave the young servant, Gaap willingly changes their game to a challenge where Yasu must find the criminal of the story while reading mystery novels. If Yasu could find out the tricks and the criminal before reading the solutions, Yasu and the human side would win; failure would mean that the witch and the magical side won and the case would become a fantasy novel drowning the darkness of magic.
One day, Gaap took possession of Yasu's body to play a prank on a servant; amazed by the beauty of magic, Yasu decided to become a witch as well. Yasu took on the name Beatrice and the title of the Endless Golden Witch, transfering to Beatrice some of the witch's characteristics such as her cackling laugh and the butterfly minions, while Gaap would become a new witch (nameless until Beato could think of a name) and Beatrice's friend in the golden "paradise". Gaap gains her name only after Beatrice meets Maria, who gives Gaap her current name and her role as a demon. Afterward, Gaap is depicted as she is in all the previous games in the series.
In response to a magician's demands, she gives the power of instant movement. She always uses this wonderful power for pranks. Hiding keys and bags during busy mornings is her specialty. However, this power becomes a final weapon which can easily strike the finishing blow in closed room mysteries. Her queen bee-like attack would probably pierce all famous detectives, making them surrender.
- As stated in The Lesser Key of Solomon, Gaap is a mighty prince and Great President of Hell who is the prince and king of southern region of Earth and Hell. He controls water, as the ruler of the water demons. Yet another one of his powers is "carrying and re-carrying men from different locations," which is the ability used in this series.
- According to Answer to the Golden Witch, Gaap is a personification of the idea that "things often vanish," then became a Witch.