Heine Wittgenstein, an adult male standing at 155 cm, is routinely mistaken for a child due to his youthful appearance. His distinctive features include dark salmon-red hair, reddish-amber eyes, pale skin, and thin silver-rimmed rectangular glasses. He consistently wears a black cap with white and gold lining featuring a white tassel, paired with a long black jacket bearing burgundy and white accents. His ensemble includes a dark brown vest, white collared shirt, black tie with a gold tip, fitted black pants, and heeled ankle boots.

Heine exhibits extreme stoicism and minimal emotional expression, though he maintains unwavering politeness even when delivering insults. Beneath his reserved exterior lies profound empathy and insight. References to his height or childlike appearance provoke strong reactions, as he considers them personal slights. Exceptionally intelligent and multitalented, he avoids showcasing his abilities but lacks artistic skill and inhabits a notoriously cluttered living space overrun with books.

His background diverges between continuities. In the manga, Heine led the non-lethal mafia Heinrich Family, advocating for oppressed kvels and immigrants in Glanzreich. When subordinates attempted to assassinate Prince Viktor during a covert outing, Heine intervened but was wrongly imprisoned after Viktor sustained injuries. Facing execution for prior vigilantism, Heine accepted his sentence until Viktor—post-recovery—secured his release by appointing him royal tutor to learn about societal injustices.

The anime offers an alternate origin: Heine led street children and befriended Viktor during the prince’s unauthorized palace excursions. Guards mistook their interaction for kidnapping when spotting a royal pocketwatch in Heine’s possession. During their escape, Viktor took a near-fatal rifle shot meant for Heine. Enraged, Heine attacked the guards but stopped at Viktor’s plea. Imprisoned for kidnapping and attempted regicide despite innocence, Heine prayed solely for Viktor’s recovery. After the prince awoke and explained the truth, Heine was pardoned. Viktor later built a church where Heine taught street children before his tutorship.

In both versions, Heine accepted the royal tutor role under King Viktor’s condition to resign if his past became public. Tasked with educating princes Kai, Bruno, Leonhard, and Licht, he employed stern, tailored methods addressing their insecurities through intellectual challenges, emotional support, and occasional psychological manipulation, steadily earning their respect. His combat skills—honed from his past—emerged during protective acts like subduing bullies threatening Kai.

When his criminal history was exposed in court, Heine tendered his resignation. The princes defended him passionately, citing his integrity and their trust, leading Viktor to reject the resignation. This acceptance drew rare emotional displays from Heine, including tears of relief. His commitment extended beyond academics to molding the princes into compassionate leaders capable of eradicating ethnic discrimination, reflecting his lifelong dedication to marginalized communities like the kvels.

Distinctive traits include vocalizing sound effects during movements, aversion to alcohol, and a close, trusting relationship with Viktor rooted in mutual respect. Despite his reserve, he occasionally displays dry humor, particularly when teasing Licht. His journey culminated in witnessing the princes mature into principled individuals committed to societal equality, fulfilling his vision for Glanzreich.