|Name in Japanese||セラフィム|
|Voice Actor (Japanese)|| Shizuka Itō (Drama CD)|
Yōko Hikasa (Anime)
|Voice Actor (English)||Morgan Garrett|
|Debut (Anime)||Episode 02|
|Debut (Light Novel)||Volume 01|
|Debut (Manga)||Chapter 01|
|Appears in||Light Novel, Drama CD, Anime, Manga|
Seraphim (セラフィム, Serafimu?) is a vampire ninja (吸血忍者, kyūketsu ninja?), and is now living with Ayumu Aikawa, due to wanting to be Eucliwood Hellscythe's servant, although since Ayumu has taken the position, she is now surprisingly Ayumu's servant, however she doesn't act, or like being called his servant at all.
She initially received a mission to take Eucliwood to her village. Later she received another mission to kill Eucliwood for luring out the Megalo into the Human World. However, the mission was later revoked, since the gates of the Underworld has been sealed. As such she continued serving under Eucliwood.
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, such as 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" (クソ虫, kusomushi?, lit. "dung beetle"), or "disgusting", mainly because of him being a pervert. Despite being rude she does shown concern for his well being when she volunteered to help fight with Ayumu twice against Kyoko and the King of the Night. As well in episode 11 where she was worried if Ayumu would ever wake up after losing Eu. She has shown to care very much of Eu. Despite her loyalty as a vampire ninja, she later given up on the mission to kill Eu by her superiors. Also as a vampire, she periodically requires blood to stay alive, and can anesthetize people with a kiss in order to numb the pain from neck bites (she does this with other girls, since kissing a boy would symbolize marriage in her cult's rules).
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. In season 2, she turns out to be a tsundere and imply that she is in love with Ayumu, as she becomes more friendly than hostile, but she still believes Ayumu has dense perversions as she punished him in episode 9 (season 2) when Naegleria was on top of Ayumu accidentally.
The Vampire on Ayumu's Doorstep
Seraphim arrives at the Aikawa residence after a long time of searching for Eucliwood's whereabouts. She instantly states her purpose of coming over — requesting Eucliwood to take her in as a servant — but was quickly rejected. This does not stop Seraphim to stay overnight at Ayumu's house; in fact, she is careful about Ayumu stealing the position of Eucliwood's servant from her, so she wants to test Ayumu to see if he is worthy of getting such a position.
The fight between Seraphim and Ayumu concluded with Sera deciding to become Ayumu's servant instead. However, she is not ready to become friendly with him immediately. She soon joins Eucliwood and Haruna as Ayumu's companions in the Aikawa residence.
During the course of her stay, she helps in fighting against Megalo and hangs out with Ayumu and her fellow housemates.
- Teleportation : She can disappear in a rustle of leaves and reappear elsewhere in another rustle of leaves, it also appears that she can carry this with her during the teleportation.
- Tsubamegaeshi Sword Style: She is a formidable swords-woman, 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 mistook the name of the violin for spaghetti), she uses the violin to destroy a large number of Megalo/spirits that appear after the King of the Night uses Eucliwood to open a gateway to hell. This ability is the outcome of her having sucked the blood of Eucliwood's.
- Lighting Spell: Dragon Fang Thunder Thrust.
- She was killed by Yoruno in season 1 episode 10, only to be revived 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.
- Her sword technique name is likely a reference to the famous Japanese swordsman Sasaki Kojirō and his famous technique, the Swallow Cut. It was said to be so quick and precise it could cut down a bird mid-flight. However, no description of the technique is given.
- Kyoko reveals, in her appearance in season 2 appearance, that Sera is "attached" to Ayumu, hinting to the viewer that she may be masking her feelings for him.
- Her name is likely a reference to the Hebrew word spelled exactly the same in the Latin Alphabet. Seraphim is the plural of seraph, which literally translates to "burning one," and is the name of the highest order of angels.
- She's a terrible cook and would often subject Ayumu to her food.
- Her favourite food is Miso soup.
- Though she is a vampire and does consume blood, Sera can be seen eating regular food.
- Sera is shown to be proficient in household chores and can be seen doing the laundry from time to time.
- Most of her clothes tend to reveal her large bust.
- She is a tsundere and very much hides her true feelings, especially when it comes to Ayumu.
- She stands 173 cm (5' 7") tall, and weighs 62 kg (141 lbs). Her three sizes are 100-62-98.
- Despite being a Vampire, she can see her reflection in a mirror, as seen in episode 8.