"Ryuuichi is the male protagonist in the manga ""Sick Yandere Prince Depends on Me to Continue His Life"". He is a member of the royal family and currently the crown prince. His name is mentioned multiple times throughout the series, as he plays a significant role in the story.

Ryuuichi is portrayed as a sickly and frail prince who heavily relies on the main female character to assist him in his daily activities. He suffers from an unnamed illness that requires constant medical attention and medication. As a result, he has a weak constitution and is often bedridden.

Despite his physical limitations, Ryuuichi possesses a sharp mind and a kind heart. He is gentle and considerate towards those around him, especially towards the main female character who takes care of him. He is grateful for her assistance and often expresses his gratitude towards her.

Ryuuichi is also depicted as a yandere character, meaning he has obsessive and possessive tendencies towards the main female character. He becomes jealous and protective of her, often leading him to take extreme measures to keep her close to him. However, he never intentionally harms her and genuinely cares about her wellbeing.

In terms of appearance, Ryuuichi is depicted as an attractive young man. He has short black hair and blue eyes. He is often seen wearing a traditional royal attire, consisting of a white kimono with a red overlay.

Overall, Ryuuichi's character plays a significant role in the manga ""Sick Yandere Prince Depends on Me to Continue His Life"". He is a complex character with both weaknesses and strengths, making him an interesting and dynamic character to follow."