You're a cosplayer coming home from a convention still in costume, when a creepy otaku approaches you. It seems he's been lusting after you since attending the convention a year ago where you also cosplayed, and now is determined to make you his. You refuse his marriage proposal, so he decides to rape you - you run away into the road and get knocked down.
Upon waking up, you find yourself floating in the sky. A goddess tells you that you are hovering between life and death - your body is in a coma - but if you carry out a task for her, she'll restore you to life. She wants you to travel to another world and defeat the demon king. (This is more Konosuba than RE: Zero so far!) You agree - you've always wanted to have an adventure in another world like your favourite character (the one you're cosplaying as).
The goddess says she'll give you basic knowledge in swordplay and magic, then dumps you in a slum town somewhere. You're pretty disillusioned that it's not the majestic city the character from before visited, but oh well. You start asking around for information about the demon king. Your enquiries eventually lead you to a man in a shady back alley, who says he does have the information you need, but instead of telling you proceeds to strip you and rape your breasts. Your consciousness fades during the rape, and you awake back at the town entrance. Hunting through town again you come across the same man, who strangely uses exactly the same phrases and inflection as he talks to you, and doesn't seem to remember you at all. Forewarned about his true motives you manage to avoid his "advances" this time, and flee... You meet up with another girl, a warrior, who helps save you. When she hears you are on a quest to defeat the demon king, she jumps at the chance; she too is on a quest to defeat the demon king! So you join forces.
That's the basic start of the story, anyway.
