Can't Retire So They Sent Me to School

At 17, Rain Shepherd, a foxkin and the world's top-ranked Magicmaster, completes a decade of battlefield service fighting Fiends and monsters and asks to retire. His superiors refuse to lose their strongest asset, sending him to a magical academy under a hidden identity to learn ordinary life and build bonds while remaining on call for major threats. Rain lives alone in a large private residence, researches and invents magic, crafts lighter stronger gear from defeated enemies, and struggles with common sense, trust, love, and squad life after always fighting alone. The headmaster knows his true rank, while students are ranked in the hundreds or thousands by talent, grades, and kill count, and the school and military organize people into four-person squads.