Aliza is Sans and Frisk's daughter, born on the surface and raised by her grandmother, after Frisk's death. Like her great- grandmother before her (Aliza the first) she is kind and adventurous, with an iron force of will. She is a spunky, largely positive girl thrust into a world of mayhem and madness and ruin. Her life on the surface wasn’t much better, from her learning disabilities to the abuse she suffered from her guardian to her guilt over the manner of her birth; as such, she makes the best of what she can, and does her best to survive. The mysterious magic running in her veins assists her, as ever it did in times of danger, and brings her to a revelation of enormous proportions… that she wasn’t as alone as she had once thought.
Frisk was pregnant with Aliza during her time in a mental institution. No one knew she was pregnant until she started to show physical signs and an ultrasound was done. Frisk's estranged mother pressed charges against the asylum for giving Frisk heavy medication while pregnant, even though no testing showed she had been.
After Aliza's birth, Frisk died, leaving the newborn in her grandmother's care.
Aliza's grandmother insisted on homeschooling her, but after a few years gave up the effort when her own mind started to slip, leaving Aliza with a poor education. With her limited reading skills and weak eyes, Aliza finds reading difficult and humiliating. She reads her journal with a magnifying glass.