Falin Touden is the younger sister of Laios Touden, and her disappearance into the depths of a dungeon serves as the primary catalyst for the party's journey. She is a young woman of twenty-three years, born on December 1st in the Northern Continent, and stands approximately 170 centimeters tall. Her appearance is marked by fair skin, amber eyes, and uneven, light-brown hair. From a young age, Falin has been nearsighted, which led to a habitual squint as she often narrows her eyes to see more clearly.

In terms of personality, Falin is defined by a profound and encompassing kindness. She is a gentle, caring, and considerate individual who actively avoids causing harm to others, even extending this compassion to the restless dead. When encountering ghosts, she prefers to cast wards to circumvent them rather than dispelling them, reasoning that banished spirits would only reform later after undergoing needless suffering. This empathetic nature is balanced by a highly self-sacrificing and occasionally reckless streak. When the lives of her loved ones are in danger, Falin does not hesitate to act or place herself in harm's way to protect them.

Sharing her brother Laios's fanatical interest in biology, Falin possesses a unique curiosity about all living things, including monsters and insects that others might find repulsive. Rather than being disgusted by the idea of consuming monsters, she is often amazed and excited by it. This peculiar fascination is a core part of her character. Her motivations are driven by a desire to protect those close to her and a genuine, almost academic passion for understanding the natural world, even its most dangerous corners. Her favorite foods include fruit and cream, and she reportedly does not dislike any particular food.

Professionally, Falin is a talented magician. Her magical abilities are exceptional, particularly in the areas of support magic, healing, and exorcism. She possesses strong defensive and priest-like spells and has a natural talent for spiritual affairs, often approaching spirits with compassion rather than force. Her approach to magic is intuitive and sensory rather than strictly logical, which makes her a poor teacher despite her immense skill. While she prefers to avoid direct physical combat, she is not physically weak and has demonstrated the ability to defend herself with a heavy morning star when necessary.

Falin's role in the story is both as the initial objective and a tragic figure. Early on, she sacrifices herself to a Red Dragon to save her party, casting a teleportation spell to send her companions to safety as she is consumed. Later, she is resurrected by her friend Marcille using ancient magic, but the combination of black magic and dragon flesh leaves her vulnerable. She is subsequently captured and transformed into a chimera by the Lunatic Magician, her soul merged with that of the Red Dragon, turning her into a powerful but controlled servant who attacks her former friends. Her development throughout the narrative involves her transition from a supportive party member to a tragic antagonist and eventually to a victim in need of saving once more.

Her key relationships are central to her character. She shares a very close bond with her elder brother, Laios, having grown up together and sharing a common interest in biology. She often helps smooth over his social blunders. Her friendship with Marcille, which began at the Magic Academy, is another vital connection. Marcille was initially impressed by Falin's unique perspective on dungeon ecosystems, and the two became fast friends, with Marcille holding Falin in very high regard. Another party member, Shuro, fell in love with Falin after witnessing her fascination with insects, though this affection was ultimately not returned. Her relationships are built on mutual respect, admiration, and a deep, unwavering loyalty that Falin herself embodies through her self-sacrificing actions.