Rasuna Sumita works as an assistant at manga studio G-PRO under protagonist Kakushi Gotou. She is a young woman with wavy hip-length whitish-gray hair, swept bangs, and olive green eyes, typically dressed in a white shirt and long pink pants.

Diligent and relentlessly positive, she strives to excel in her duties. Colleagues view her as the studio’s most upbeat member; she rarely complains about her workload or the need to hide Kakushi’s secret profession. Scenes occasionally position her for fanservice, emphasizing her figure or featuring a shower sequence.

Her name derives from "sumi tarasu na" ("don’t drop ink"), reflecting her creative role. The surname Sumita combines "sumi" (ink) and "ta" (field), while Rasuna comes from "ra" (gauze/thin silk) and "suna" (sand/grit). She initially joined G-PRO for its proximity to Daikanyama and her interest in creative work.

Throughout the narrative, including flash-forwards, she remains committed to guarding Kakushi’s secret from his daughter. Years later, her conduct implies she maintained this discretion when questioned. During Kakushi’s coma, she achieved her career goal by debuting as a manga artist with an original work.

The theatrical edition integrates her into its expanded narrative, adding scenes and an extended conclusion. It continues exploring secrecy and family dynamics, with Rasuna persisting in her supportive role at G-PRO.