Lena attends Rem Elementary School alongside Jin and Akira, sharing their fascination with demons and the unknown despite lacking demon-summoning abilities as an ordinary human. Her discovery of a demon-summoning book in the school library ignites the central plot, drawing intense interest from Jin, Akira, and transfer student Amy Kashihara. This book ultimately exposes Jin and Akira's hidden identities as Devil Children.

In Valhalla, Lena actively supports the Rebel faction and participates in missions alongside Shin. During a critical operation, Imperium forces capture and execute her—a death later reversed when Darklord and Lord Light resurrect her, marking a pivotal narrative moment. The anime adaptation shifts her personality from adventurous to timid, depicting her desire to abandon Valhalla and evade combat entirely.

Later media plunges Lena into brainwashing and manipulation. Throughout Devil Children Fire Book and Ice Book, antagonists transform her into an Angel Child. Under the false Enoch's command, she is transported to Niflheim and attacks Jin alongside angelic allies like Remiel. Similarly, the Light & Dark anime sees her brainwashed by the archangel Enoch, with the finale revealing her continued manipulation persisting beyond Enoch's apparent defeat.

In Devil Children Messiah Riser, Lena accompanies Jin through Valhalla but falls into enemy captivity. Jin rescues her during a subsequent mission. Within Light & Dark's game mechanics, she appears as a C-Rank opponent in the BattleNet arena. Defeating her seven times rewards players with Nikare, while twenty-eight additional victories grant Undine.