Kakeru Otori is Naru Otori's older brother; their relationship is somewhat strained and distant, though neither seems particularly troubled by this dynamic. He features across multiple narrative threads, primarily within bar and street vignettes.

In the bar vignette, Kakeru frequents Alexander, establishing himself as a ladies' man and a close friend of Shūsuke Chitose. He occasionally assists Shūsuke by reading manuscripts and engages in his own freelance writing, characterized by a free-spirited, whimsical approach rather than discipline. His personality here is typically cold, aloof, and reserved, displaying a distinct dislike for intrusive social interactions, especially from women. He often speaks bluntly and insults freely, yet shows restraint around Shūsuke, whom he enjoys teasing and finds amusement in Shūsuke's embarrassing situations.

Conversely, Kakeru adopts a radically different persona as "Phoenix," the founder and leader of the dominant Yanagihara gang, the Yanagihara Flame Birds (YFB), controlling the area's nightlife. In this role, he exhibits an impulsive, hot-tempered, and thrill-seeking nature, actively pursuing fights and enduring injuries for the adrenaline rush. This shift is visually represented in the anime by his blond hair and red eyes as the YFB leader. His leadership involves navigating conflicts, like tense confrontations with the rival gang R-Wings.

Kakeru possesses a split personality disorder, initially presented as two distinct individuals sharing the same name before being revealed as different aspects of the same person. As the series progresses, the separation between his personalities becomes less defined by specific vignettes. His interactions with Eriko Hino are notably dismissive and condescending, reflecting his aversion to unwanted attention. Kakeru demonstrates awareness of the main male protagonists' shared secret condition and occasionally collaborates with them, particularly in efforts to aid Takashi Haneda, who remains unaware of these connections.