A man who was reincarnated in another world as a 9th class wizard and retired after saving the continent from a dragon war. He decides to open a small restaurant in the countryside, but his routine is anything but ordinary. On the second floor of his restaurant, there lives a black dragon who has transformed into a woman, named Rurin. She is greedy, cute and loyal to him, but also ignorant and clueless about the human world. They live a fun and warm life, serving customers, solving problems and growing violets in the garden.
On his deathbed, the Great Philosopher expressed remorse, as he was never able to learn magic. Five hundred years later, he was reborn as Mazel Loran, the son of a feudal lord. His family believe him to be a late bloomer in terms of his magic, but also think he’s the next incarnation of the Great Philosopher. But Mazel has a secret that nobody else knows: while he does not have any magic, he has experience with “physics”!
\"Healing magicians cannot fight alone.\" Keyaru, who was bound by this common knowledge, was exploited again and again by others. But one day, he noticed what lay beyond healing magic, and was convinced that a healing magician was the strongest class. However, by the time he realized that potential, he was deprived of everything. Thus, he used healing magic on the world itself to go back four years, deciding to redo everything.