This is the kingdom of AOA. It is where the angels including Yui came from.

There are several conditions for an angel to die.

1. If he/she loses all the feather in his/her wings
2. If she/he accepted a mission but failed to succeed.
3. If he/she fell in love with a human

There 5 different kinds of angel in AOA. Let’s rank them accordingly.

Kýrios – he/she is the head master of AOA. She/he is the most powerful angel for she/he can revive an angel according to his/her choice.

Igétis – they are the leader of every obóz in AOA. They control the flow of their obóz.

Umpire – They work in the court of AOA. If an angel abides a rules stated in AFA or Authority for Angels, they are the ones who decide for the punishment.

Warrior – They are the soldiers of AOA. They fight against the kingdom of Ferno for they want to reincarnate the angels and turn them into human.

Obróncá – They are also called guardian. They are the angels responsible for guiding a human that is listed in the Kathalogos ton Anthropinon or The List of Mortal.

Terminologies 

Oboz - A camp in AOA. There 6 oboz in the Kingdom namely : Yeol ; Baek ; Suho ; Hun; Kai ; Soo

Ferno - Another Kingdom that promotes reincarnation

Nato - It is a necklace of the angels. They naturally have it but it will only appear if the angel is about to die.

Synopsis

Do you believe that angels exist? Some yes , others no. Well here’s a story of an angel from the Kingdom of AOA who was sent to guide a human being. She must fulfill her mission for her to become an Umpire, or else she will face her own death. Will a playful and trouble-maker angel melt the cold heart of a human? WIll she succeed without falling in love with him?

Characters

Yui - She's the head Obronca  of Camp Yeol.She was sent by the Kyrios to guide a certain guy on Earth. If she will be able to fulfill her mission, she will be promoted as an Umpire of Camp Yeol.

Kris - A college student in SM University. His exceptional handsome features made him popular inside the campus. His charisma caputres the heart of every girl. He grew up without his parents so he is very independent. He is also the team captain of their university's Basketball Team.