Little is known about Tsukasa’s early life, and she intentionally avoids discussing her past. However, several clues throughout the series suggest that she is not an ordinary human. She demonstrates deep familiarity with ancient texts, cultural eras long past, and even forgotten forms of technology. Her physical resilience such as walking away unscathed from a traffic accident that nearly killed Nasa further hints at something supernatural.

While her origins remain unconfirmed for much of the story, Tsukasa appears to have lived through many generations of history, retaining a youthful appearance despite seemingly having knowledge spanning centuries. Her decision to marry Nasa marks a pivotal change in her life, suggesting that for the first time in a long while, she desires to live not just quietly, but happily with someone who truly sees and accepts her as she is.

Tsukasa is a petite girl with pinkish hair, often styled in a side ponytail or worn loosely. Her most striking features are her calm golden eyes and soft facial expressions that convey wisdom and serenity far beyond her years. She has a gentle, timeless beauty that makes her seem both modern and ancient at once.

She typically dresses in modest, casual clothing suited to daily life, often wearing hoodies, skirts, or simple dresses. Despite her plain wardrobe, she carries herself with grace and elegance. Her ageless appearance often causes others to question her background, though Tsukasa herself remains unfazed by these curiosities.

Tsukasa is calm, thoughtful, and emotionally reserved, often keeping her deeper feelings to herself. She comes off as mature and composed, with a dry sense of humor and a subtle, playful sarcasm that balances Nasa’s earnestness. Though initially hesitant to show emotion, she gradually begins to express warmth, affection, and even a bit of mischief as she becomes more comfortable in her married life.

While she is generally level-headed, Tsukasa has a strong sense of justice and will not hesitate to stand up for those she cares about. Her love for retro films, classic literature, and quiet hobbies like stargazing further reflect her introspective nature. Underneath her mystery, she yearns for connection, and through her relationship with Nasa, she learns to embrace emotional intimacy.

• Saving Nasa and Initiating the Marriage
  Tsukasa first appears when she saves Nasa Yuzaki from being hit by a truck, taking the full brunt of the impact herself yet emerging uninjured. When Nasa confesses his love, she agrees to be with him on the condition that they marry. She later returns to him with marriage documents, officially becoming his wife and setting the tone for a story about love that begins after the vows.

• Adjusting to Domestic Life
  Though initially aloof, Tsukasa grows accustomed to daily married life with Nasa. She handles household duties, shares quiet moments with him, and slowly opens her heart. Her reactions to modern conveniences like smartphones and online shopping are often subtly comedic, highlighting her unfamiliarity with the contemporary world.

• Hints of an Immortal Past
  As the story unfolds, characters like Chitose Kaginoji and others from Tsukasa’s past suggest that she may be far older than she appears. Tsukasa deflects these questions but drops clues about a long and possibly immortal existence. Her knowledge of historical events and media from every era hints at a tragic, enduring loneliness that she has only begun to overcome through her bond with Nasa.