Maggie gains a demon that symbolizes lust at age 11, which is a common age for girls to enter puberty. Gil gains a demon symbolizing envy only after his beautiful planet is destroyed, he loses his family, and he is enrolled in a highly competitive boarding school.
In chapter 4 Ava wakes up with bandages on her over her clothes. The person who wrapped her, Gil, says he wants to be a doctor and has been studying for several years now. It seems like a typical example of Worst Aid except we find out his files has him listed as a medical janitor not doctor.