神无月的巫女 (Kannazuki no Miko)

Plot

Shy Himeko adores Chikane, the gorgeous and cool "princess" of their exclusive boarding school. She's been looking forward to their joint sweet sixteen birthday party for weeks. But on that fateful day, a shrine appears in the sky, giant robots ravage the school, and Himeko discovers that she is the reincarnation of the Solar Priestess and Chikane is the reincarnated Lunar Priestess. As dark secrets unravel, one thing is clear: their lives will never be the same.