Shirabe Ako

Ako is one of Sōta's classmates.

Personality
Ako is very down to earth and towards the start she's a bit closed off, though she opens up a bit more later on.

Shirabe Otokichi
Otokichi is Ako's grandfather, and she's been living with him.

Minamino Sōta
They're classmates and friends.

Hōjō Hibiki
Ako has been a bit dismissive of Hibiki at times.

Mephisto
While Ako could not approve of Mephisto's actions, she didn't want to fight her father either, though she eventually did so when she realized it was the best way to help him. Mephisto is quite the doting father, perhaps excessively so.

Noise
When Noise was in the form of a small bird, Ako took him in and named him Pī-chan, treating him as a pet.

Etymology
Her surname, Shirabe (調辺), is likely based on the word 調べ (shirabe), which can mean either investigation or tune, the latter most likely being what the writers had in mind, although the former is also fitting in a way as Hibiki and Kanade had tried to investigate the identity of Cure Muse.

Her given name, Ako (アコ), could be intended as a reference to the Japanese word アコギ (akogi), a short form of アコースティックギター (akōsutikku gitā), meaning acoustic guitar.