Ai Astin

Ai Astin (アイ・アスティン) is a 13-year-old (as of episode Class 3-4 II) human-Grave Keeper hybrid. She is quite naive, but cares a lot about others. She calls Hampnie Hambert her "father" due to something her supposed mother had told her when she was younger, and decides to follow him on his journey.

Appearance
Ai has a very fragile and small look to her body and face, with a flat chest, long goldish-brown hair, and big bright green eyes. She looks more like a younger version of Alfa, with messier hair as the bangs that fall beside her cheeks have a few strands being longer then the others, unlike her mothers whose hair is well kept and neat with Cleopatra style cropped bangs beside her cheeks.

Personality
Ai is a very out going girl. She tries her hardest to fill her mother's shoes as a Grave Keeper and to please everyone in the village. However, as seen in Episode 1, she can get very emotional at times which could lead to her being put in dangerous situations.

Background
Ai is a human-grave keeper, who took the role of the Grave Keeper of the village after her mother Alfa's death.

Hampnie Hambert (Ai's "father")
He acted quite cruelly towards Ai but actually loved her and protected her. It is revealed at the end of episode 3 that Hampnie is in fact her birth father.After his death they bonded with each other creating a close relationship.

Julie (Yuri)
Julie is a friend of Hampnie Hambert whose wife and child both died. With Ai, Scar (another Grave Keeper) and Celica (Ulla's elder sister), they travel in a minibus, meeting major characters Alis Color and Dee, Ulla and Kiriko. Ai occasionally likes to tease him about his relationship with Scar later in the series.

Ulla
Ulla and Ai become friends almost immediately after Ai goes to see what she's like. They like to tease Kiriko and have conversations with each other. Although Ai revealed to Ulla that she wasn't dead, Ulla didn't seem to be upset by it since she did know for a time that something was off. Ulla is sadden by the fact that she can't look at Ai or hug her, but they manage to hug each other through Kiriko. It is shown that Ai still keeps in contact with her and Kiriko as she writes them a letter about her travels so far.

Alis Color
Alis and Ai seem to have a special bond, both wanting to save the world (in different ways, as seen in episode 11). Dee appears to be quite jealous of their relationship, as she loves Alis and doesn't want to live in a world without him. Dee confesses her love for Alis to Ai and also reveals her secret.

Ai and Alis also have certain moments when they are alone together, like after everyone celebrated Alis' birthday on the road (episode 9); on the balcony after Ai's birthday (episode 11); on the basketball court (episode 11 and 12) and when they embrace he kissed Ai's forehead in episode 12.

When Alis is talking to Ai on the balcony about Dee, he goes somewhat towards breaking point, knowing he killed his fellow classmates with his hands. He believes that he crossed a boundary that no human being should cross. Ai tells him that it's not true and says: "Alis, you're...", which snaps Alis out of it. It is not sure what Ai was going to say to him, but she probably was going to say something out of concern for him since she cares deeply for him as well.

Dee
Dee and Ai are good friends. Dee gets jealous due to the attention that Ai gets from Alis. Ai cares deeply for Dee shown in Episode 11 and 12 when she doesn't want Dee to disappear. Ai also doesn't tell Alis about Dee's secrets since Dee wanted to tell Alis herself. Although Ai tends to be with Alis more, it is unknown whether she has romantic feelings for him like Dee does.

Trivia

 * As Hampnie stated, she is not a true "Grave Keeper" because she has parents and negative feelings toward him. However after meeting Scar soon after that, it is confirmed that she is a Grave Keeper.
 * She is one of the last child born in the world about 12 years ago.
 * Ai is a half Grave Keeper and half human due to her mother, Alfa, being a Grave Keeper with emotions.
 * It seems that her powers may transcend from that of a gravekeeper, as she brings Alis back from the dead, though this could have also been the result of a wish she had, which would confirm the idea that a strong enough wish had been granted.