Lanna is a quiet and soft-spoken girl from High Harbor, a surviving island where a simple society has redeveloped in close contact with nature. She is the granddaughter of Dr. Lao, a scientist who created a powerful solar energy technology that was used in the war that devastated the world. Lanna is deeply devoted to her grandfather, who has gone into hiding to prevent his invention from being weaponized again. She is about eleven years old, with dark violet hair and black eyes.

Lanna's initial role in the story is that of a catalyst for the adventure. She is discovered by Conan washed up unconscious on the shore of Remnant Island, the first person his own age he has ever met. She was fleeing from agents of Industria, a militaristic and technologically dependent society that wants to capture her and use her as a hostage to force Dr. Lao to reactivate the solar power system. Her arrival shatters Conan's isolated existence and sets him on a journey to rescue her and protect her from those who would exploit her.

Her personality is characterized by gentleness, resilience, and a quiet inner strength. She is initially portrayed as a damsel in distress, but throughout the series she reveals a deeper courage and determination. She never gives in to the threats of Industria, and her unwavering faith in Conan remains a constant source of hope. She serves as a moral compass, representing the innocent, nature-connected side of humanity that contrasts with Industria's cold, industrial dystopia. Her motivation is to protect her grandfather and prevent solar energy from being used for destructive purposes, as well as to reunite with Conan and build a peaceful future.

Her key relationship is with Conan. The two form an inseparable bond built on trust and mutual care. Lanna has an absolute belief that Conan will always survive and come to save her, no matter how dire the circumstances. This trust is depicted in several silent but powerful scenes, such as when she smiles at the sight of him coming to rescue her from captivity. She also shares a close bond with her grandfather, Dr. Lao, and has a special connection with nature, particularly with seagulls.

Lanna possesses a notable ability: she has telepathic communication with seagulls. She can send and receive messages with them, and she often uses a particular seagull named Tikki as her ally and messenger. This ability is inherited from her grandfather and proves crucial at several points, such as when she telepathically warns Conan of an impending disaster. In addition, she displays intuitive understanding of natural phenomena and is attuned to the world around her.

Over the course of the story, Lanna undergoes noticeable development. She matures from a frightened girl who is initially captured and helpless into a brave, determined young woman who actively participates in her own rescue and the fight for a better world. She learns to stand up for herself and others, and she grows into a leader who risks her life for Conan and the cause of peace. By the end of the series, the once innocent and sheltered girl has gained experience and confidence, and she and Conan set sail together to build a new world that preserves the positive aspects of the past while avoiding the mistakes that led to destruction.