Princess Silver reigns as the sole heir to the Crayon Kingdom's throne and the direct ancestor of its legendary hero, Queen Buretsu, who once imprisoned the Grim Reaper within a mirror. Her reign as the kingdom's only child cultivated twelve notorious flaws: excessive focus on fashion, chronic messiness, habitual lateness, dishonesty, raucous and temperamental laughter, boastfulness, greed, picky eating, stubbornness, stinginess, deflecting blame, and suspiciousness. These traits deeply troubled her caretakers, especially the Chameleon Prime Minister, who feared public exposure would tarnish the kingdom's image.

Her journey begins abruptly during her twelfth birthday celebration. A quarrel with a mysterious boy who refused to dance with her resulted in her parents being transformed into stone statues. Convinced only the Grim Reaper could reverse the curse, Silver launches a perilous quest to find him. She is joined by two low-ranking castle guards: Stonston, a perpetually hungry pig, and Araessa, an orphaned rooster raised by a tigress. Mistakenly believing the boy who petrified her parents is the Grim Reaper in disguise, she remains unaware they are distinct individuals. The Grim Reaper actively pursues her, seeking vengeance for his imprisonment by her ancestor.

The quest reveals the boy as Prince Cloud, who petrified the king and queen to shield them from the Grim Reaper. He reluctantly joins Silver's group. Their dynamic is defined by constant friction and mutual annoyance, fueled by Cloud's blunt critiques of her flaws. Despite frequently declaring hatred for him, Silver harbors romantic feelings, finding him handsome and experiencing moments of blushing admiration. She once confided in Araessa about having "fallen in love once but decided never to do so again," with Prince Cloud immediately surfacing in her thoughts. Their interactions include shared moments tinged with romance, often shattered when Silver realizes his compliments mask backhanded insults.

Silver's core development involves conquering her twelve bad habits, essential to defeating the Grim Reaper. This arduous process forces her to confront selfishness and learn genuine care for others, including her companions and the twelve magical vegetable spirits residing in her perfume compact. These spirits aid her when summoned, providing clues and magical assistance. The journey catalyzes her maturation from a spoiled royal to someone capable of bravery and self-sacrifice, particularly when her friends are endangered. Key triumphs include reassembling shattered mirror fragments to discover the Grim Reaper's weakness—tickling under his left arm—and using a lock of his hair to restore her parents.

Following this victory, a new challenge emerges when Silver's cat maid, Punya, accidentally frees two mischievous angels. Silver embarks on another journey alongside Prince Cloud, Stonston, and Araessa to retrieve them, though Cloud's presence becomes less consistent. This leads to ongoing travels across the kingdom, reflecting her sustained growth and dedication to her duties.