Hyakuren no Haou to Seiyaku no Valkyria (Novel)

Yuuto Suoh gets more than he bargained for when he joins his childhood friend Mitsuki Shimoya in testing out an urban legend: When he uses his phone to take a picture of himself with the local shrine's divine mirror, he is whisked off into another world — one heavily steeped in the lore of Norse myths. Using his knowledge gained from school and his solar-powered smartphone, he has the chance to bring the Wolf Clan, thepeople who cared for him, to prominence, all while earning the adoration of a group of magic-wielding warrior maidens known as the Einherjar. **