[Harry Potter] Old Friends

A thousand years later, the Wizarding World is peaceful and calm. The Dark Lord has been defeated, life has returned to normal, and children are happily learning and growing up at Hogwarts. But they don't know that the first headmaster of Hogwarts is the caretaker who makes his nightly rounds, that the head of Slytherin, who stands at the pinnacle of power on the European continent, is their librarian, or that the daughter of one of the Four Founders, Ravenclaw, is in fact the administrator of the Sago official forum. Unheard-of people and unheard-of happenings: memories and secrets from a thousand years ago slowly unfold before them. A new world and future lie ahead, and they encounter legends from an unknown age.

The setting is carried over into this sequel, set a thousand years later, when the grandchildren's generation is attending school. It's basically the story of two thousand-year-old bachelors showing off their affection without even realizing it, while quietly keeping their accomplishments hidden behind the scenes.