It has not been directly mentioned in the show description but, because of my extended family experience with it, my assessment of Yan Mo is that he has some sort of autism spectrum disorder (ASD, probably Asperger's). I love that the story is based on real life and the manner in which the characters have been written and portrayed. Living and loving someone with ASD can be challenging at times (as shown by the awkward moments sprinkled throughout and this show really highlights that it is possible with the right partner.