Seraphim is a girl with long black hair and green eyes. She ties her hair in a high ponytail and leaves a few locks of hair to dangle on either side of her face.
Sera possesses glamorous proportions, and is very well-endowed. She usually wears clothing that emphasizes her breasts, including sleeveless blouses with thin shoulder straps.
She has an obsession over the Tsubamegaeshi Sword Style, and is constantly seen praising it. She is shown to be quite rude, especially to Ayumu, constantly calling him a piece of shit, or disgusting. Despite being rude she does shown concern for his well being when she volunteer to help fight with Ayumu twice against Kyoko and the King of the Night. As well in Ep.11 where she was worried if Ayumu would ever wake up after losing Yuu. She has shown to care very much of Yuu. Despite her loyalty as a Vampire Ninja, she later given up on the mission to kill Yuu by her superiors.
She also plays the violin and is very dedicated to learning how to cook. Although the food always taste horrible and causes Ayumu to faint.
- Leaf Transformation: As shown in her fight between her and Ayumu. She is capable of turning herself into leaves, and is able to escape harm by doing so. She is then able to reform back to her original form.
- Tsubamegaeshi Sword Style: She is a formidable swordswoman, keeping someone like Ayumu Aikawa on his toes, she has a preference of using the Tsubamegaeshi Sword Style (燕返し, lit. "Swallow Reversal"). This sword style revolves on the usage of leaves in combat, including the use of a katana made out of leaves and phasing through attacks using leaves.
- Ninjutsu: She is also knowledgeable in ninja techniques, including the usage of logs to escape attacks.
- Red Energy Blasts: She has shown the ability to create red crescent energy blasts to attack the opponent.
- Devil Wings: She can use devil wings to fly in combat and out of combat.
- Violin: After being given a violin by Haruna (who mistakes the name of the violin for spaghetti), she uses the violin to destroy a large number of megalo/spirits that appear after the Lord of Darkness uses Euciliwood to open a gateway to hell. This ability is the outcome of her having sucked the blood of Yuu.
- She is killed by Yoruno in season 1 episode 10, only to come back to life when Eu pricks her own finger to supply blood for her in which Eucliwood's blood will ultimately make her the key to sealing the gates of the underworld