They are generally awful.
The woman is startled and pure and generally behaves like some fruit hit her on the head. Or, the actors try their best to hide their faces with their hair or hands or with long-distance camera shots. Or, the camera shows weird angles to hide touching because of the show rating. Or, the actors look like testing for fever (like mothers do, touching a kid's face with their lips). Or, the the ML or the FL look too young and it's uncomfortable to watch an adult person kissing an underage person. Or, the kiss scene is quite realistic and it lasts for several minutes and nobody cares about the writing, the plot holes or the development of the action any more. Or, the actors don't really match as professionals and they don't look natural at all when they play in the same scene. Pretiness doesn't guarantee talent and professionalism.
In some dramas, the kissing scenes happen at the appropriate time in the story, in a realistic timing for a couple to kiss and in a believable way. Those scenes don't ruin the episodes, but they are very rare in all the asian dramas I've watched. In general, from my observation, kissing scenes are either too "innocent" or too "staged".
What I really hate, is the man grabbing the unsuspecting woman and going for her mouth (yes, this is what it looks like when badly staged) and she staring at him in enchanted surprise.