I don't know what else to say but this K-drama is awesome, in terms of story, actors, ost, everything is perfect.
The story a man losing his memory/returning like a 7 year old child until he regains his memory, going through really tough times.
and stories of romance, family, affection, all presented very well, especially the story between mother and child which really brings tears to my eyes. You have to watch this and guaranteed you won't regret it??