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. She wears a straw hat that covers the back of her head.

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.

Story
After Hampnie Hambart shot up her entire village, he forced her to bury all of the dead, dejectedly, she does what she is told. Hampnie later tells her that she isn't a real gravekeeper, as gravekeepers don't have emotions, which was later unconfirmed as another grave keeper, Scar, confirmed Ai was indeed, half gravekeeper.

After the encounter with Scar, Hampnie tells Ai to forget all about the village, which she refuses to, which causes Hampnie to angrily pull a gun on her and threaten to shoot her. Right before he does, Yuri comes and protects Ai. During this match, Ai learns about Hampnie's "Immortality" and former friendship with Yuri, as they plan a duel the next day.

After the encounter, Ai goes along with Hampnie and gets a piggyback ride to escape from Yuri faster, revealing that Hampnie indeed didn't want to fight Yuri. That night later, Hampnie and Ai bond with eachother, as Hampnie tells her of his past life, and mentioning how school is a living hell. When Hampnie mentions he wants to die a happy man, then mentions himself a monster, Ai then realizes that her father never wanted to be mentioned as a human, as he didn't want to be "the last man alive"

The next day, Hampnie and Ai continue on their journey, when Hampnie realizes something in the distance. He swiftly pushes Ai off of the bridge they were walking on and fights in the ensuing battle. Ai is later rescued by Yuri, who informs her of what is going on. They both, along with Scar, attempt to rescue Hampnie from a gang, lead by the undead Hiko.

After defeating Hiko's gang, Hampnie finally realizes that he is indeed Ai's father. Hampnie, in his last human words, gives Ai her last name and reveals himself as Kizuna Astin. After he reincarnates, Kizuna and Ai spend the rest of the day together, as Kizuna decides to disregard his morals, just this once. After the day of fun, Ai buries her father under the watch of Scar and Yuri. Ai's quest is now to save the world.

The next day, Ai, Yuri and Scar go on their journey in an abandoned car, in which Scar manages to find a sleeping Kiriko, who just fled from bandits. After the realization, the three attempt to wake him up, in which he just falls right back asleep again, while mumbling, Kiriko reveals about a distant city in which he serves under a princess. After Kiriko finally wakes up, he asks them to drop him off at Ortus, which the three agree to. As Ai despirately tries to convince Yuri to go to Ortus for a bit, Scar realizes that it's a place filled with the undead. The car in the end, needed repairs due to continuous malfunctioning, in which Kiriko tells Yuri that the city of Ortus can repair it. The four make it to Ortus, in which Ai gets a quite "welcoming" introduction by Pox, an immigration officer. Pox agrees to allow them to stay in Ortus for a bit as thanks for bringing Kiriko back.

During the visit to Ortus, Scar falls ill and Ai offers to take care of her. Scar declines, and Ai decides to discover the city of the dead for herself. Ai meets a maid, who gives her a mask to visit the city. During all the fun, she finds Kiriko, and discovers he is one of the deceased, and learns about Princess Kuroshiohake (Ulla), learning that she is indeed a living person while talking to her on the top of the Ortus tower. As Ai realizes this, she goes back to the hotel room, in which she tells the information to Julie and Scar, who is still sick. Kiriko soon tells the group that the city is under martial law, as there are people who are suicidal and want to become citizens of Ortus. She soon realizes that Ulla is Ortus's mass murderer, and it is likely that the city is using her for this. When they meet again on the tower, upon convincing Kiriko, Ulla confesses to her and Kiriko that she knew all along, but wanted to end the suffering of others for their sake, as it makes her happy. Soon after this, Scar gets cured of her Phantom pregnancy by adopting Celica, who called her from the tower whilst frozen in time.

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 daughter both died. With Ai, Scar (another Grave Keeper) and Celica (Ulla's older sister), they travel in a minibus, meeting the main characters Alis Color and Dee, Ulla and Kiriko. Sometimes they occasionally like to tease him about his relationship with Scar, as later seen 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 have a special bond, both want to save the world (in different ways, as seen in episode 11). Dee seems to be very jealous of their relationship, since she loves Alis and does not 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 small moments when they are alone together, after everyone celebrates Alis' birthday on the way (episode 9); on the balcony after Ai's birthday (episode 11); on the basketball court (episode 11 and 12) and when they embrace Alis kissed Ai's forehead in the epidemic 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 children 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.