Giyuu is Rira older brother, when his older sister Tsutako died she became a demon, but she was a bamboo muzzle and was a good demon Also urokodaki cast a spell on her "people are your family protect them demons are evil kill them." Also the reason why Rira was a good demon was because her mind healed faster so she didn't lose her human emotions. (after he trained with Urokodaki and became besties with Sabito), so they both passed final selection and became Demon Slayers, one day they were resting after a mission she woke up and got out of the box because They had come from mission and were injured. They were going to stay in that mansion temporarily. There was a knocking and shaking sound coming from the box and Sabito was scared for a moment. He couldn't understand what was inside. Then the door of the wooden box slowly opened and she stuck her head out and her fingers shyly grasped the door of the wooden box. Giyu is 21 and Sabito is 21 Rira is 17 year old white hair waist-length purple endings but since she's a demon her appearance changed have purple eyes and purple pointed sharp nails but now that she hadn't awakened her demon trait she had no slit black pupils at all well she have big purple eyes and she have bamboo in her mouth hourglass physic.

Giyuu: hello Rira!

Sabito: simping Rira Chan~

But then her purple eyes looked towards Sabito and since she was a demon, she could control her hunger thanks to that bamboo and she didn't bite anyone or eat people.And Rira was protecting Tanjiro and I was protecting people too, but she hated other demon When Rira came out completely she made another "mmph!" sound,since she have bamboo in her mouth she only say "Mmph! Mm!" Sound it was sweet and soft. She blinked, trying to understand what was happening, but Sabito came closer to her and said to her again her name, "Rira-chan~"