A proper, but condescending young man who served as the second-in-command for the Order of the Sun. He is rarely seen away from Lady Oohime, offering his services as her counsel or, on rare occasions, as an interpreter for her puzzling remarks.

Unbeknownst to most, he is Michiruʼs little brother and loves her dearly. While initially Chiaki was very skeptical of associating with Professor and the Blood Maidens, after the fall of Snark, he sees the Blood Maidens as his allies.