Succubus Runa and the Erotic Dungeon

While heading home, the protagonist, Runa, is caught in sudden rain and - decides to take a bath and go to bed, but finds herself in a strange space. - When she exits the space, she is suggested to become a "magic soldier" by an old man and young assistant. - With no choice, she is forced to fight monsters she had never seen before.?? - Damage can't be done by swords or axes to monsters of this world, and without guns,? - the only weapon that could damage the monsters was "that" - Runa changes her name to "Legendary Succubus Runa", solves the mystery of this world, - and to return home, goes to a dungeon filled with monsters all alone.​