It appears to be another case of blowing things out of proportion.  Seo In Guk recently appeared on tvN's 'Taxi' and responded to the MCs' question by saying he found Yoon Sae In the prettiest female co-star he has worked with so far.  They had previously acted in drama 'Rascal Sons' together.  

This has attracted a lot of attention from people who were perhaps even thinking there was more to this casual statement, enough so that Seo In Guk's agency, Jellyfish Entertainment, had to put such suspicions to rest.

SEE ALSO: Which female co-star does Seo In Guk find prettiest + would he ever do a same-sex kiss scene?

The rep said, "He only said she was pretty in response to a question asked on the show, but it has become an unexpectedly hot topic . . . Yoon Sae In and Seo In Guk acted as husband and wife in the drama, but they are only on friendly terms."

He continued, "He got her contact information at the time they were filming the drama, but we know she has changed her number since.  Seo In Guk does not even know Yoon Sae In's new phone number."