Undine are generally one of the more fragile races, but absolute terrors if the fight ends up on or near water. Their water magic, as with that of Halkegenia, naturally lends itself to healing, and some Undine may possess a similar affinity to the Sylphs, able to track the flow of fluids within the body and sense out abnormalities. They tend to prefer cooler and damper climates.
- An Ice Person: Their combat arsenal centers on ice.
- The Medic: The Undine specialties are healing and buff spells.
Leader of the Undines, Count of OrleinFormer Leader of the Aincrad Liberation Army and now a Faery of the Undine race. He logged into ALO to aid in the <<Asuna Rescue Mission>> at Argo's request, hoping that the knowledge he had gleaned through his MMO Today connections might be of use in finding an exploit to crack <<The Grand Quest>>. He and his fiancee Yulier are caught in the rioting that occurs immediately after the transition in Orlein but manage to calm about half of the city's population, quickly taking control of the crises and working with the officers of the decapitated faction. Upon seeing Thinker's effectiveness for himself, Lord Mortimer requests that he attend to administering Orlein in the absence of the Faction Leader. After it becomes clear that the transition may be permanent, Thinker and Yulier accept the situation and choose to act as examples to prove that life can go on.
- Henpecked Husband: Jensen jokes that Yulier becoming Thinker's wife also makes her the real leader of the Undines. I.e. "All hail Lady Yulier".
- You Are in Command Now: He takes up the position in the absence of Undine faction leaders.
YulierA former member of the Aincrad Liberation Army and now a Faery of the Undine race. Yulier logged into ALO to help with the <<Asuna Rescue Mission>>, along with her fiancée Thinker. After the transition, Yulier quickly takes up her old role as Thinker's Lieutenant and aids in the management of Orlein. After it becomes clear that the transition may be permanent, Thinker and Yulier accept the situation and choose to act as examples to prove that life can go on.
JensenA former police officer and member of the Arrun City Watch. He is assigned by Lord Mortimer to investigate Novair's murder.
- Fire-Forged Friends: He was dismissive of Argo initially but after working and cracking a case with her he becomes much more friendly with her.
- Get a Room!: Argo's Nav Pixie tells both of them this after their compliments get a little flirtatious.
- Skeptic No Longer: Being transported across worlds and being plugged into a fairy's body does wonders to open one's mind, it seems.
Irene (Tsushima Namiko)An elementary school teacher before the Transition. She is now the primary teacher in Arrun Home, concentrating on local history and language, in addition to several science subjects.
- Bread, Eggs, Breaded Eggs: While contemplating the phrase "when in doubt, do what you can", the narration from Irene's perspective notes that what she knows is "teaching, and children, and how to teach children".
- Older Than They Look: She has a teenage body, but she was 50 when the Transition happened.
- Parental Substitute: She's taken it upon herself to mother all the children that were caught in the Transition without older relatives to take care of them.
- Parasol of Prettiness: In keeping her motif of a classy Yamato Nadeshiko, she carries a parasol when going out during the day.
- Ship Tease With Shoichi Saitou, by way of her interest in him specifically tutoring her in healing First Aid, and also relating to an older gentleman like him.
- Yamato Nadeshiko: She is a classy Japanese woman, both modest and gentle. Her build is slender, even delicate, and she wears a kimono as her usual outfit. This belies remarkable courage and fortitude. When the Transition occurred, she flew between the fairy cities searching for displaced children, gathered them together in Arrun and created a safe place where they could be looked after and provided for. Judging by Bardiche's introduction, she is good at keeping them all in line.