Lulala Heine lives as a mermaid in Lindworm's Merrow Waterways district. Her father abandoned the family, leaving her responsible for supporting her mother and three younger siblings. She provides income by spending excessive time above water singing for tourists, straining her health.

Physically petite with warm-toned, tan skin, Lulala possesses honey-blonde hair, teal eyes, and distinct mermaid traits. These include a vertically oriented tail fin striped vibrant yellow, white, and black; webbed fingers; gills below her ribcage; webbed ears; and white fins tipped with black along her arms. She typically wears a white bikini top with an orange hood and skirt, the skirt featuring teal gemstone tassels. White ribbons wrap her arms, ending in orange frills at the wrists. Her youthful stature often causes others to mistake her age, which matches Glenn Litbeit's.

Lulala exhibits a selfless, brave, and slightly tomboyish personality. She works tirelessly to sustain her family, refusing to let health limitations deter her duties. Confident in her abilities, especially her singing, she reacts with irritation when others question her capabilities or treat her condescendingly due to her appearance. Her courage is evident when she rescues a drowning boy despite her own compromised gills, nearly drowning herself. After Glenn saves her, she develops a shy, evasive crush, often blushing and avoiding him. She maintains graciousness and kindness toward Glenn, never displaying aggression or possessiveness.

Her abilities include:
- **Amphibious Breathing**: Breathing both air and water using lungs and gills. Prolonged air exposure inflames her gills, impairing underwater breathing and risking drowning.
- **Singing**: Possessing exceptional vocal talent, she captivates audiences through skill, funding her family's needs. She sings exclusively in English despite speaking Japanese.
- **Hydrokinetic Blast**: Generating high-pressure water streams powerful enough to incapacitate adversaries or break solid obstacles.
- **Enhanced Swimming**: Demonstrating remarkable strength in water, capable of feats like single-handedly pulling a gondola against strong currents while carrying multiple passengers.

Key relationships shape her story:
- **Glenn Litbeit**: She develops a one-sided romantic interest after he treats her inflamed gills and saves her. Glenn views her professionally as a patient and friend.
- **Saphentite Neikes**: Sharing a sisterly bond, Sapphee often acts protectively. Lulala occasionally bribes Glenn's sister, Sioux, seeking approval as a potential spouse.
- **Skadi Dragenfelt**: Receiving patronage and assignments from Lindworm's chairwoman, she undertakes missions with fierce loyalty.

Trivia notes:
- Her design draws inspiration from the lemon tetra fish.
- She briefly withstands freshwater spray from fountains without gill damage.
- Her family never appears directly, though their circumstances drive her actions.