When a show starts with sex it usually means that it is planned to be one long climax.
Sorta like the problem of incurring a 4 hour you know.
After a while it ceases to be a good time.
You are better off switching the channel and watching reruns.
Another reason I watch Korean shows online... often they don;t even hold hands until the 8th episode and they might kiss before the final episode. Sometimes.