The experiment was nothing but a simple marriage experiment. 

To see how these couples would in their own ways deal with things. 

Takuya and Joonjae, they were playing a gay couple. Their professor wanted to see how they would be able to live after moving into an apartment building where most people viewed their love as wrong. 

The thing is, only Takuya and Joonjae knew this was an experiment. Their professor wanted real results.