Tsubame, known regionally as Sonam, is a recurring kunoichi and Hattori's classmate from Iga Province. She possesses a round face with rosy cheeks, black hair in a ponytail often adorned by a flower accessory, and wears distinctive pink ninja robes with purple gloves.

Gobby, bossy, meticulous, headstrong, and edgy, Tsubame frequently loses her temper over minor issues and exhibits a prissy, perfectionist attitude, particularly in household matters. Despite this, she is fundamentally friendly, caring, and helpful, often assisting Kenichi's mother. Her primary loyalty is to Hattori, whom she openly adores and wishes to marry, though he keeps reciprocal feelings discreet.

Tsubame initially clashes with Kenichi, Shinzo, and Shishimaru. Mistaking Kenichi for a burglar in his first appearance, she binds and gags him, sparking a physical confrontation with Shinzo and Shishimaru. Hattori intervenes, calms her, and facilitates introductions. This encounter leads to ongoing trouble caused by her fastidiousness until the group collectively drives her back to Iga. Over time, she transitions from antagonist to trusted ally, forming genuine friendships with Kenichi, Shinzo, and Shishimaru.

She harbors strong dislike for Kemumaki and his ninja cat Kagechiyo, though they occasionally collaborate in attempts to outmaneuver Hattori. Beyond ninjutsu, Tsubame is proficient with woodwind instruments, owning a bassoon, flute, recorder, piccolo, and clarinet.

Her development shows a shift from initial hostility to integration within the main group. She maintains her spirited demeanor while channeling meticulousness into supportive actions. Her enduring infatuation with Hattori remains consistent, though she demonstrates broader loyalty to the group over time.