Wataru, a member of the idol group Callings, exudes a mischievous charm that masks his sharp perceptiveness, often causing others to underestimate him. His playful antics and trickster persona contrast with an uncanny ability to read hidden emotions, particularly those of Mion Takamine, toward whom he nurtures unreciprocated affection. While his flirtatious teasing toward her remains lighthearted, he steadfastly supports her during vulnerable moments—shielding her from unwanted advances or offering solace in times of distress.

Early narratives highlight his approachable nature, tutoring Rizumu Amamiya in English and joining summer festivals to connect beyond his idol circle. His evolving appearance mirrors personal growth: short red-brown hair gradually lengthens into a style tied back with a black headband, signaling maturity.

Three years later, he maintains active involvement with Callings while adopting a more assertive role in guiding peers, such as urging Shou to confront romantic tensions. A glimpsed future reveals him collaborating with Mion at Pretty Top, seamlessly transitioning into Jun’s former mentorship role—a testament to his loyalty and professional evolution from supportive friend to trusted partner.

His name, meaning "to spread," aligns with Callings’ thematic concept of "an echoing show." Manga-exclusive lore assigns him the surname Hyuuga, though this remains absent elsewhere. While his past lacks elaboration, his unwavering presence anchors Mion and others, blending humor with heartfelt reliability to stabilize those around him.