Based on the erotic game by Effordom Soft.

Since childhood, our protagonist Kaname has always dreamed of becoming a Knight. After a near-fatal terrorist attack nearly killed both him and a new-found friend, they make a childhood promise that one day they’ll meet again in their quest to become splendid Knights that can protect others. Now, many years later, Kaname is about to enter a special school run by his father, where he and his younger sister Yuu (a big-brother-loving genius who skipped a grade to be with him) will be part of a special Knights-in training club called “Esquire”. On his way to school, though, he spots a mugging on the street from outside his bus window as they drove by, and with little hesitation he opens the bus window and jumps out of the moving bus to help. As part of the effort to solve this crime, he runs into the other heroines who will all eventually end up being the fellow members of Esquire. As the only boy in this club otherwise full of girls, will Kaname be able to fulfill his childhood promise? And will he and the “boy” with whom he made that promise ever meet again as they vowed?