Nagomi Shiraishi is a first-year high school student in the same class as Minato Nagase. She possesses short pink hair, blue eyes, and a petite stature, standing 144 cm tall with an A-cup bust measurement. An ahoge (cowlick) is often visible, and she typically wears her school uniform, sometimes adding ribbons or a coat. Her personality is mysterious and enigmatic. She makes unpredictable appearances in various locations without explanation. Her behavior and technological skill strongly suggest she may be an alien. She is reserved, sly, mischievous, and prone to breaking the fourth wall, frequently engaging in cryptic or manipulative interactions with others, punctuated by her dry, biting "Fu-Fu-Fu-Fu" laughter. Nagomi is tasked with monitoring and potentially disrupting the engagement between Junichi Nagase and Yuuhi Katagiri. She focuses particularly on Junichi's actions, observing him closely and suggesting his behavior toward Yuuhi is suspicious. Surveillance equipment in her living space implies covert activities. She shares a friendly relationship with Minato and accepts the nickname "Nago-Nago" from peers. In the anime adaptation's finale, two identical Nagomi figures appear, indicating she might have a twin sister or uses a robotic duplicate for observation. During the *Hardcore* OVA, Nagomi joins other characters on a trip to a private island. While the episode features comedic and risqué scenarios involving special sunscreen, her mysterious demeanor remains consistent. Her interactions with Junichi hint at an unconventional friendship. Her overarching motives stay unresolved.