Momona, a shy and reserved middle school student from the human world with low self-confidence about her ordinary background, finds her life transformed at her cousin Alto's wedding. Lady Diana, the bride, approaches her, leading to Momona's sudden transport to Jewel Land and her selection as a Petite Lady candidate by the Jewelpet Ruby. This event propels her journey to become a noble lady, a path she doubts she belongs in due to her perceived normalcy.

Her personality blends scatterbrained tendencies and quiet determination. She displays clumsiness and initial social awkwardness, often feeling isolated. However, inspired by her admiration for Lady Diana, she persistently strives to improve her skills. Momona harbors a love for desserts and hot dogs, with the latter highlighted as a trademark preference. Over time, she evolves into a more confident individual, fueled by developing relationships. Key traits include stubbornness, occasional obliviousness to her surroundings, and unconventional problem-solving approaches during tests.

Physically, Momona possesses bright pink hair styled in large twin buns with side tufts, secured by a prominent light pink polka-dotted bow. Her casual attire includes a pink-and-white shirt, red tie, black skirt, pink sweater tied at the waist, white socks, and brown loafers, often accessorized with a beaded bracelet. Her formal Lady outfit is a floor-length pink Victorian-style dress adorned with hot pink bows, ruffles, and a heart-shaped detail at the chest.

Her romantic arc centers on Cayenne, beginning with an accidental kiss during a fall at their first meeting. Their relationship evolves from mutual belligerence and denial of feelings to deep affection, complicated by rivalries with Lillian (Cayenne's sister) and Elena. Significant moments include near-kisses, jealousy, and a heartfelt goodbye when Cayenne departs for the Royal Palace, motivating Momona to advance her studies. They ultimately marry after sacrificing their memories to save Jewel Land using the Final Wand, later regaining them and restarting their relationship.

Interpersonally, Momona forms close bonds with fellow Petite Ladies: the tomboyish Mizuki, the bookish Charon, and her initial rival, Lillian. Her dynamic with Lillian shifts from cold competitiveness—fueled by Lillian's possessiveness over Cayenne—to genuine friendship and supportive rivalry. She also navigates affections from Romeo, who partners with her during tasks and later confesses his feelings (which she declines), and Miura, whose flirtations fade as he shifts his interest to Lillian.

Her development culminates in profound heroism. In the series finale, she delivers a persuasive speech to the emotion-consuming Beasts about inherent human goodness, convincing them to cease destruction. Alongside Cayenne, she then uses the Final Wand, sacrificing her life temporarily to restore peace. Post-revival, she loses memories of Jewel Land but later reunites with Cayenne in the human world. Her story concludes with their marriage and her stated aspiration to become a baker.