Eien no Aselia is a visual novel produced by Xuse (formerly Honjouzou). A fan translation was created by Dakkodango Translations and also released by JAST Densestu. It is now available on Steam under the title Aselia the Eternal.
Takamine Yuuto was an ordinary high schooler until he is teleported into the world of Phantasmagoria. He is then enslaved by the King of Rakios and forces him to fight in wars of expansionism, because the ruler holds his sister Kaori as a hostage.
Eien no Aselia is a turn based strategy game, where the player controls squads composed of 3 units, each having the role of attacking, defending and using spells.
By capturing towns and defeating enemy squads, Mana is gathered and it can be refined into Ether. The ether is then used to build building and mostly to increase the power of existing units.