Crown Prince Tsukasa Tenma of Tanoshimi is the eldest child and only son of the Tenma family. He tries to be a supportive brother to his frail younger sister, Saki, and constantly worries for her health, although he would never admit that. He is in a relationship with the royal alchemist's son, Rui Kamishiro, however he wishes to keep it secret out of fear he will be disowned. He is in an arranged engagement with Nene Kusanagi, torn between genuinely loving her and resenting their arrangement.