One

Ever since Matthew was young, his parents have always left him alone in their big house to go on business trips. He hates it, but hides it, knowing that him telling them won't fix anything. Thankfully, ever since he got a boyfriend a few months ago, he has started staying over at his place whenever his parents are gone.

What happens when his boyfriend's twin brother, Kim Jiwoong, comes back from abroad, and Matthew has had a little too much to drink, not even being aware his boyfriend has a twin?

And what happens when the next day, he and Jiwoong, both wake up with a timer on their wrist, indicating they only have 30 days until it stops. They're not sure what the timer is for, but the only way to stop it is whenever they're together.