Phantom Dream Series by Natsuki Takaya

Tamaki Otoya is the last in a line of ancient summoners tasked to battle against evil forces that threaten mankind. Burdened by his duty as a summoner, Tamaki has always found strength from his childhood friend Asahi. That is until Asahi goes missing and reemerges as the descendent of the very group that Tamaki is destined to destroy."

The jahoutsukai returns to collect the Suigekka - the demon sword Tamaki's family stole from the Gekka family to prevent them from acquiring more power. He also reveals some devastating family secrets to Tamaki."

Asahi truly defected to the Gekka - but why? What other secrets are hidden in the past, and when the factions of the Gekka and the Otoya begin to shift, where will Eiji's loyalties fall?"

Tamaki Otoya is the last in a line of ancient summoners tasked to battle evil forces that threaten mankind. Burdened by his duty as a summoner, Tamaki has always found strength from his childhood friend Asahi, with whom he has a deep, emotional bond. So when Asahi's friend is found out to be possessed by a demon, he awakensas the one destined to exorcise demons out of tortured human souls...

Tamaki Otoya is the last in a line of ancient summoners tasked to battle against evil forces that threaten mankind. Burdened by his duty as a summoner, Tamaki has always found strength from his childhood friend Asahi. That is until Asahi goes missing and reemerges as the descendent of the very group that Tamaki is destined to destroy.