Aselia the Eternal

Yuuto has been raising his step-sister Kaori since they lost their parents, and the two of them have built a difficult but stable life. That ends when they are both pulled through a dimensional gate into a parallel world they will come to know as Phantasmagoria. Yuuto cannot understand a word anyone speaks here. Kaori is taken prisoner immediately and labeled an asset. Her captors label Yuuto an Etranger and force him to fight using a sword that seems designed to gradually bend its wielder's will. What starts as pure desperation — fighting solely to reach Kaori — shifts over time as Yuuto genuinely begins to care about the spirits who fight alongside him and about the fate of the world that has claimed him.