Yonaki Uguisu

Yonaki is Ahiru's lover, she came to Parano with him but was capture by the King. She then was kept in a birdcage in the throne room of Elephant castle for the King liked listening to her singing, and as hostage to ensure Ahiru obedience.

When the King was beaten, she was liberated by Ahiru, when given the choice to go through the Door to Heaven they decided to stay in Parano and to never be separated again.

Her name means "nightingale", which fit her as she is trapped like a caged bird.

Appearance
She is a young woman, with long hair.

While she is the King hostage she wore a Brown coat over a white dress, it's unknown if she is wearing the same attire at that time, but when she is rescued, Haruhiro notes that she was forced to wear clothing which made her look like a bird.

Personality
Before Parano she was a strong but sensible woman, who wasn't afraid to be honest about what she thinks of other.

Spending a long time as the king hostage in the disturbing world that is Parano she seems to have grown weaker and according to Kuzaku only look a shell of a person while in cage.

Once rescued by Ahiru she seems to get more lively once again.

Before Parano
She was the first women that Ahiru truly loved, meeting her profoundly changed him.

Sometimes after meeting, they decided to go on a journey without destination together, it during that journey that they ended up in Parano.

Finally, sometime before volume 14 she was capture by the King.

Level. 13 Heart, Open, A New Door
She is only mentioned by Alice when talking to Ahiru in Ruins No.6, but the mere mention of her name is enough to put Ahiru on edge, likely because of his inability to do anything to rescue her.

Level. 14 Parano-mania
Kusaku sees her in her beard cage in the throne room of Elephant Castle, and the King threaten Ahiru to kill her a few time.

She is finally rescued after Team Haruhiro, Team Io, Alice, and Ahiru defeat the king.

When given the choice to go through the Door to Heaven they decided to stay in Parano and to never be separated again.

Abilities
She is a great singer both Ahiru and the King finding her singing delightful.

Like everyone in Parano she should able to use magic, but while nothing in know about the type of magic she can use, it's likely nothing special as she was powerless before the king.

Ahiru
He is madly in love with her and she seems to feel similarly as they choose to stay together in Parano.

Kuzaku also notes that while held hostage in the throne room she looks like a only a shell of a person she start to move when she notice Ahiru.

Ahiru call her by a nickname: "Yuiko".

The King
He took her as hostage and "pet bird", but she seems to be nothing but a toy to him as he threaten to kill her multiple times. Moreover, when Alice and their allies come to attack the king he declare that he has just grown tired of Yonaki's singing and that he could make a shadow out of her.

It's unknown what Yonaki think of the King but as she was waiting for Ahiru to come save her, she likely hates him.

Quotes

 * "Yoshiharu, I believed in you!" - Yonaki only line, Volume 14