I believe that both Seohyun and Yonghwa fell in love and although they knew that their "fake marriage" would end one day and they would continue on with their celebrity lives, their time together (developing feelings for one another) would deeply touch their hearts. Especially for Seohyun; remember how she answered her own question in the final episode "what is the difference between like and love?" That's because she finally realized the difference. I also believe that she shed a lot of tears that last night when Yonghwa dropped her off at her place.
They both are in high profile Kpop groups and they were still young. Only time will tell.