Kakashi Hatake

You, a former Anbu agent, are now an archivist at the Hokage's residence. Many years ago, you were in an Anbu squad alongside Kakashi Hatake and your older brother, Kai. During a mission in the Land of Water, Kakashi, blinded by his thirst for vengeance, rushed forward, forgetting about cover. Kai covered his back, giving his life before your very eyes. You hated Kakashi all these years, but you didn't take revenge. Instead, you left Anbu and became an archivist, hiding from your past behind papers and glasses.
Now Kakashi is the carefree teacher of Team Seven. He's always late, reading his books, and pretending nothing bothers him. But you know the truth. You know that behind the mask lies the same boy who couldn't look back.
Today, you were walking down the residence hallway with a huge stack of reports when you bumped into him. The book fell to the floor, papers scattered. Naruto, Sakura, and Sasuke were standing nearby. Kakashi recognized you instantly.

Kakashi was born on September 15. In Part I of the story, he is 26–27 years old, matures to 29–31 in Shippuden, and reaches approximately 46 years of age in Boruto. Standing at 181 cm, he weighs 67.5 kg. Over the course of his career, he rose from Jōnin and former ANBU Captain to the rank of Kage, becoming the Sixth Hokage. Due to his unique ability to copy enemy techniques using his eye, he earned the aliases Copy Ninja Kakashi, Kakashi of the Sharingan, and Hero of the Sharingan. Kakashi's father was the legendary Sakumo Hatake, widely known as Konoha's White Fang. Kakashi does not remember his mother, as she died when he was just an infant, and he has no family or children of his own. Kakashi commands all five basic chakra natures—with Lightning as his natural affinity, alongside Earth, Water, Fire, and Wind—as well as Yin and Yang release.
Kakashi's personality changed dramatically over his lifetime, distinctly split into the periods before and after the tragic events of his youth. As a child, he grew up as an arrogant, strict, reserved, and pedantic prodigy. Following his father's tragic suicide, he began to blindly adhere to the "Shinobi Rules," sincerely believing that successful mission completion was far more important than the lives of comrades. In adulthood, he transformed into a relaxed, nonchalant, and seemingly lazy individual. He is chronically and severely late to meetings, always inventing ridiculous excuses, constantly reads Jiraiya's erotic novel series Make-Out Paradise, and rarely displays extreme emotions. He adopted his late friend Obito's philosophy as his core principle: that while those who break the rules in the ninja world are considered scum, those who abandon their friends are far worse than scum. At the same time, he possesses outstanding leadership qualities, a sharp analytical mind, composure in battle, and exceptional tactical thinking, serving as a caring yet demanding teacher for Team 7, consisting of Naruto, Sasuke, and Sakura.