Duo
The following day, rumors of Tooru and Julie had spread like wildfire. The two, the only boy-girl duo in the year, become quick friends with Tomoe and Miyabi at breakfast. After they had a strange and weird lesson on the rules and basics, the class then went onto training. More misunderstandings were made by Tomoe. After that, they went onto sparring. Due to Julie's remarkable talent in sparring, no one other than Tooru volunteered to spar with her. The end of the week has come and Tooru had discovered that Julie still doesn't have a Duo after Tomoe's rejection so he runs after her and with the sounds of the bells on her hairband, he finds her standing on the balcony of the clock tower. It was there that they made their Duo oath to each other and became a Duo...
Aired 11/01/2015EP 2 - Duo

Absolute Duo
The story begins with Blaze — a weapon that is the manifestation of a human's soul. Tooru Kokonoe happens to be qualified for this, but for some reason his Blaze is not a weapon, but a shield. Moreover, he enrolled in a school that teaches combat skills, and thanks to the school's Duo partner system, he ends up living with a beautiful silver-haired girl.
(Source: Anime News Network)