Phone Braver 3, also known as Third, is the third of the seven Phone Braver units, the small robots that transform between mobile phone and active robot forms and were developed for the protection of people and computer networks. In the series he is assigned as the official partner, or buddy, of Daiki Kirihara, an Under Anchor agent who came to the organization from a career in the police. Kirihara is a former officer who disliked technology and joined Under Anchor in part to prove himself wrong about that feeling. This background shapes the partnership, as the severe and outspoken Kirihara is paired with a robot whose manner could hardly be more different.

Third's personality is defined by his calm, self-effacing courtesy. He is humble in bearing and polite in speech at all times, using a formal and respectful tone even in tense situations. Where Kirihara is cool, blunt, and quick to aim sarcasm and cutting remarks at others, especially younger agents such as Keita Amishima, Third habitually smooths over those remarks, gently compensating for the friction his partner creates. His restrained and accommodating demeanor makes him a natural counterweight to Kirihara during their missions.

In the story, Third functions primarily as Kirihara's steadying companion and support unit during Under Anchor's investigations of technology-related crime. Their working relationship illustrates the central bond between a Phone Braver and its human buddy, and the two continue to operate together across the series. The partnership also endures setbacks; after the incident known as the Parallel Decentralized Link, Kirihara was banned from missions for one month before being reinstated, after which the pair resumed their duties. Through these events, Third remains consistently composed and professionally courteous, holding to the same polite conduct whether dealing with colleagues, superiors, or people his partner has antagonized.

In terms of abilities, Third shares the standard capabilities of the Phone Braver line. He can shift between phone and robot modes, connect to machines and the internet, and access the Anchor network supervising system called Eliza for web functions and hacking, allowing him to gather information and act as an investigative tool during cases. His distinctive trait within the story, however, is not a specialized power but his manner: his unfailingly polite speech and patient temperament serve as the social counterpart to Kirihara's hardness, and this contrast is the most consistent feature of his portrayal.