Entaku no Himeshi! (円卓の姫士！) is a manga series by Tomoo Maruyama. It was serialized in Comic Birz.
When he was a child, Harada Kishi liked to play at being a knight. He swore to always be loyal to his playmate and chosen princess Shirahime Idzunu. Seven years after he was forced to move away, he has found her again at high school.
In the intervening years his enthusiasm for being her knight has not diminished, and has been fueled by otaku information. Unfortunately for him, teenage Idzunu isn't anything like his manga or anime has led him to believe princesses should look and act. To his surprise, she even takes offense at him pointing this out.
However, there is more to his knight act than he would ever have believed, as Idzuru and other girls are actually the recipients of "animus" power from falling stars. This power has transformed them into "Players" with various titles, who need to collect "Chessmen" to fight for them. Will Kishi be able to maintain his role as Idzunu's loyal knight?