Yuuto's been sent to another world, where he is now commander, or "Patriarch" of a clan of warriors.  To survive in this new world, he uses his cell phone, his only connection to the girl he loves back home.
I'll be your little sister.
Ich werde deine Schwester sein.
Seré tu hermana menor.
Seré tu hermana pequeña.
Je deviendrai ta sœur.
Sarò la tua sorellina.
Eu aceito ser sua irmã mais nova.
Я стану младшей сестрой.