Kimi kara Uketsugu Brave Chronicle

Meet Kurono Kokuya, a student in the lowest rank at Star Gate Academy – the world's cutting-edge training facility for star sorcerers, the beings who use star sorcery to protect the Earth from otherworld invasions. His childhood friend Yukihime Yukigane just happens to be the world's strongest star sorcerer, and she never lets him forget that fact. One day, their days of peace are interrupted by a powerful threat from another world. Kokuya and Yukihime stand on the front lines, risking their lives to protect those they love, but will they be able to defeat the Dark Lord Redge and his cruel minions? Source: J-Novel Club