Does 同居 have a sexual connotation? I have been watching Fate/Stay Night, the Unlimited Blade Works one. In this particular episode, as Shirou (male character) tells other characters that Saber (female character) will stay at his place, they are very surprised and use the word `{}`. The subtitles I have used the word "shack up" to translate that idiom. However, in English "shack up" has a sexual connotation : > 1. To live together and have sexual relations without being married. > 2. To live, room, or stay at a place > However, in Japanese it does not seem so : > But as the other protagonists are quite shocked at this, and that Fate/Stay Night is after all based on an erotic game, does carry a sexual connotation in colloquial Japanese ? Or is it just poor translation ?

Your observations are correct. does not necessarily imply sexual relations. For example , , and so on are perfectly natural.

(or since is not in the Joyo kanji list) is the one that does imply having sexual relations without getting married. is incorrect.

Of course, or would be actually understood as a proposal for or even marriage in great many cases, especially when this is said between a young man and a woman. I don't know the story of _Fate_ , so I can't judge if it was a bad translation.