The Fallen God! The Byakko Kogenta

Riku Tachibana seems to be an ordinary middle school student with the worries of what club to join. His unique feature is that he makes odd hand gestures, and he does not know what they really are. His childhood friend Momo-chan goes through the first of many denials of liking Riku as more than just a friend. Riku decides to ask his grandfather what the gestures mean, and soon after, he finds himself making a contract with the Shikigami, Byakko no Kogenta.