In an era where one’s soul can be morphed into a weapon, there are modern day magicians called ‘Mage-knights’. Kurogane Ikki, labelled as the is a student with particularly no talent in magic attends an institution that trains Mage-knights. Getting way less than average marks in the scorings, he was forced to repeat a year. But with the arrival of a new chairman (or was it principle?) of the institution, a new rule was created, that compatible knights (ability wise) decided by the board must share rooms and attend practice/training together throughout the school years to bring up their abilities to the max. A rule to implement the absolute verdict of ability.

By a weird (or rather expectable) turn of events, Ikki’s roommate turns out to be a princess of another foreign country called Stella Vermillion. Stella is a knight and a genius in magic who is said to only appear in a decade. ‘Walking in on her’ while she was changing her clothes caused a huge misunderstanding (since none of the sides yet knew of the new rule) which eventually ended up in a duel between the two of them. The punishment (or rather, the prize) of the loosing side is ‘Eternal Submission’ to the winning side.

The story centers around Stella and Ikki’s cohabitation. Developments and failures, all the while their relationship turns sweeter and sweeter.