Komugi Inukai, originally named Marron by her previous owner Kurihara, is a Papillon dog who escaped an animal shelter after Kurihara entered a healthcare facility. Found injured during rain by young Inukai Iroha, she was taken to a veterinary clinic and later adopted. This forged Komugi's deep loyalty to Iroha, though she retains lingering trauma from abandonment, manifesting as a strong dislike of being alone and separation anxiety. Her personality blends canine traits with human-like growth: she is naturally curious, athletic, enjoys walks, and exhibits gluttony, contrasting her earlier picky eating. However, she struggles with human social norms, often displaying childish or impulsive behavior like blurting secrets or misunderstanding games like soccer as "fetch." Despite challenges, she maintains optimism and sees good in others, including adversaries like Gaou. Her speech retains dog-like suffixes ("~wan"), and she frequently imitates Iroha's "Wonderful~" catchphrase.

Physically, Komugi has distinct features. As a dog, she has pale brown fur with darker brown accents on her ears, face, and tail, a heart-shaped patch on her head, and a curled facial lock. She wears a pink bow with a gold butterfly pendant, later replaced by a heart-designed pendant after gaining Pretty Cure powers. Her human form retains the curled lock and red eyes, with hair in a twin-segmented ponytail held by a pink bow. Outfits vary: default includes a pale pink hooded dress with magenta details and heart-shaped pockets; winter features long-sleeved hoodies and layered skirts; movie attire consists of magenta jackets and shorts. Transformed into Cure Wonderful, her hair turns pink with light yellow tips styled in twin tails resembling dog ears, eyes shift to multicolored (purple/pink/blue) with light yellow pupils, and she wears a magenta-collared dress with frilled sleeves, striped tights, and pink boots. The Diamond Ribbon Style upgrade alters her appearance: hair lengthens and thickens, the crown becomes an egg-shaped hat with wings and a magenta heart, and her dress transforms into a white gown with layered scalloped skirts, ribbon sleeves, and long white boots with purple hearts. During a temporary Gaogaon transformation induced by Gaou, her fur turns black and gray, size increases, eyes glow red, face gains a silver mask, tail becomes flame-like, and legs develop silver shackles.

Komugi's relationships define her development. Her bond with Iroha is central, viewing her as both owner and sister figure; she protects Iroha fiercely, even sacrificing herself. She cherishes Iroha's parents, eventually revealing her secret identity to them. With Satoru Toyama (Iroha's classmate), she finds solace during conflicts with Iroha and relays messages from his rabbit Daifuku, whom she befriends. She admires Mayu Nekoyashiki, entrusting her with secrets, and persistently seeks friendship with Mayu's cat Yuki despite initial friction, helping Yuki overcome trust issues. Her connection to former owner Kurihara remains affectionate—she recalls his gentle care, considers him a "grandfather," and expresses gratitude despite separation. Regarding antagonists, Komugi empathizes with Gaou/Subaru, rejecting his hatred of humans and persisting in befriending him. After Subaru attacks her, she communicates with Gaou's spirit, learning his desire to reconcile, enabling her to purify Subaru by conveying Gaou's true feelings.

Her transformation into Cure Wonderful occurs when a Garugaru attacks Iroha; Komugi's protective desire activates the Mirror Stone, creating the Wonderful Pact that grants human form and Cure powers. As Cure Wonderful, abilities include defense ("Puni Puni Barrier") and support ("Kirarin Animal Help"). Purification attacks involve physical affection: "Gyu~!" calms enraged animals via tight hugs and comforting words, generating purifying foam. With Cure Friendy, she performs "Pretty Cure Friend Liberale," using Friendly Wands to draw magical patterns and envelop targets in friendship ribbons for a joint hug purification. In Diamond Ribbon Style, group attacks like "Pretty Cure Eternal Kizuna Shower" (series) and "Pretty Cure Premiere Kizuna Shower" (movie) involve all four Cures holding hands to create bubble showers that purify enemies.

Key developments include Komugi joining Iroha's school as a human, where her naivety causes comedic mishaps but fosters connections. Mid-series, Gaou nearly transforms her into a Gaogaon, but her bond with Iroha reverses the process. During the finale, she dies shielding Iroha from Gaou but revives after encountering his spirit, subsequently losing her speech and human transformation abilities temporarily. These powers return when collective pet-owner love reactivates the Mirror Stone, affirming her role in bridging humans and animals. Her growth culminates in proving coexistence possible, directly challenging Gaou's worldview.