"Yuuka is a major character in the Japanese manga series ""Married for 120 Days."" She is introduced as the younger sister of the main character, Wataru, and one of the many women who gets married to him for a short period of time.

Yuuka is portrayed as a kind-hearted and gentle woman with a strong bond with her brother. She is very supportive of his decision to marry multiple women and even encourages him to do so. Despite having deep feelings for him, she never acts on them as she understands his desire to experience different relationships.

Throughout the series, Yuuka remains a devoted sister to Wataru and takes on the role of mediator between him and his other wives. She is also shown to have good cooking and housekeeping skills, often helping out around the household.

However, Yuuka's happiness is cut short when she develops a heart condition, forcing her to leave her husband and family behind and seek medical treatment abroad. Wataru is deeply torn as he realizes how much Yuuka means to him and how much he will miss her.

Despite her brief appearance, Yuuka leaves a lasting impact on the story and the hearts of readers with her kind personality and unwavering loyalty."