Short translation of Yahoo! Japan article on the scandal. cr.
Shukan Bunshun reports that Nogizaka46 member Matsumura Sayuri is involved in an adultery scandal. The magazine reports that Matsumura has been seeing Mr. A (alias) who works for Shueisha, one of Japan’s largest publishing companies. The two have been going to karaoke and going on dinner dates. It is also reported that Mr. A has visited Matsumura’s apartment. This Mr. A was also in charge of the gravure for Young Jump which is where the Nogizaka46 members were featured.
So that's where these two met. This might ruin Nogi's image of the clean/innocent type. But maybe there's room to doubt that Sayurin didn't know he was married w/ kids. Then again that's just a smidge hope to save her image and not paint her as the homewrecker if everything that's coming out so far is true. The guy is a sleeze in either case though.