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.
As insurance in order to make sure 
you wouldn't change your mind.
Um sicherzugehen,
dass du es dir nicht anders überlegst.
Lo hice para asegurarme de que 
no cambiaras de parecer.
Lo hice para asegurarme de que 
no cambiaras de parecer.
Je voulais garder une assurance
pour que tu ne changes pas d’avis…
Per assicurarmi che non cambiassi idea.
Era uma precaução para garantir
 que você não mudaria de ideia.
На всякий случай, чтобы ты не передумал.