As daughter of the former demon lord, Mio's foster parents were slain by powerful demons after her life. Still seeking to slay her, Basara reveals himself as a member of the hero clan--an enemy of the demons--and vows to protect Mio as a member of his family.
When you kiss the magic circle that 
forms on the back of Mio-sama's hand,
Küsst du den Magiekreis,
der sich auf Mio-samas Rückhand bildet,
El pacto se sellará cuando beses el círculo
 mágico en el dorso de la mano de Mio-sama.
El pacto se sellará cuando beses el círculo
 mágico en el dorso de la mano de Mio-sama.
Le pacte sera conclu
lorsque tu embrasseras
Quando bacerai il cerchio magico che si formerà
sul dorso della mano di Mio-sama,
Quando você beijar o selo mágico que se 
formar nas costas da mão da Mio-sama,
Когда поцелуешь появившийся на руке 
госпожи Мио магический круг,