"Tsukasa is a major character in the Japanese manga ""I Have Been Stuck On The Same Day For 3,000 Years"". She is a mysterious girl who claims to have been trapped in a time loop for thousands of years.

Tsukasa is first introduced to the protagonist, Shinichi, when he wakes up on the same day for the 3000th time. She tells him that they are the only two people who are aware of the time loop and explains that they must work together to find a way to break free from it.

Throughout the story, Tsukasa is shown to be incredibly intelligent and resourceful. She has a vast knowledge of science, history and philosophy which she uses to try and understand the nature of their situation. She also has a stoic personality, rarely showing her emotions or reacting to the events around her.

Despite her serious demeanor, Tsukasa cares deeply about Shinichi and works tirelessly to help him find a way to escape the time loop. She is also shown to have a dark and tragic past which is slowly revealed over the course of the story.

Overall, Tsukasa is a complex and multifaceted character who adds depth and intrigue to the story. Her intelligence, determination and mysterious past make her a compelling character that readers will root for until the very end."