Ais Wallenstein, also known as the Sword Princess, is a First-Class Adventurer and a key member of the Loki Familia. Among the small fraction of First-Class Adventurers, she is considered one of the strongest. Ais is a quiet person who doesn't talk much, and is bad at expressing her feelings through words. Ais is shown to be serious and merciless toward monsters during her missions. Ais is believed to be an airhead, namely due to her quiet nature. Ais is very strong-willed, doing everything to reach her goal: "to become even stronger". Ais appears to be somewhat clueless toward people confessing their love toward her, and rejects anyone asking for courtship. She also tends to react violently whenever someone does anything remotely perverted to her.

Ais entered Loki’s Familia at the age of 7. In the underground dungeon she carried everybody’s luggage. Ais was able to reach Level 2 within a year, and became the fastest person to reach Level 2 at that time, until Bell Cranel broke that record and they make up each other.