Chrono Harlaown is the son of Lindy Harlaown, an admiral in the Time-Space Administration Bureau. Serving as a commissioned officer under his mother's command aboard the spaceship Arthra, Chrono approaches his duties with extreme seriousness and strict adherence to military protocols; he addresses his mother by her rank of "Admiral" professionally, occasionally reverting to "Mother" during moments of stress. His role involves intelligence gathering and interdimensional law enforcement, frequently placing him against magical threats. Despite being 14, Chrono is recognized as one of the Arthra's most capable combat mages. He wields the Intelligent Device S2U, which typically appears as a small card but transforms into a staff-like weapon. Later, he acquires Durandal, a Device specializing in ice-based magic. Chrono's combat style prioritizes mission success, sometimes leading to harsh measures, a pragmatism stemming from limited early combat experience. Interactions with colleagues like Amy Limietta and younger mages Nanoha Takamachi and Fate Testarossa contribute to his gradual development. He gains respect for their exceptional abilities despite their age, influencing him to become more considerate in balancing duty with compassion. After events involving Precia Testarossa, Chrono's family adopts Fate, making her his adoptive sister. In the INNOCENT spin-off's alternate continuity, Chrono is an ordinary second-year middle school student at Private Tenō Middle School, viewed as an elder brother figure by the Testarossa sisters. While he previously participated with them in the virtual combat game "Brave Duel," his focus shifts toward academic responsibilities. Within Brave Duel, his primary avatar is the Executioner type, utilizing either S2U or Durandal for ice-based techniques. Chrono's character arc reflects a transition from rigid protocol adherence toward a more nuanced understanding of teamwork and empathy, influenced by relationships and operational experiences. His background consistently highlights integration into both military and familial structures, bridging TSAB responsibilities with evolving personal connections.