Long unrequited love for both of them, they end up together (ch17) with lots of misunderstandings. All is clear-up later (ch33) and they had their first time (ch36). They end-up living together. Every one have guess about them (Jeongyun family and best friend) but Jeongyun don't know it. And he don't know about Chaeheon family too. They works in the same company. But Jeongyun don't know that Chaeheon is the son of the chairman and his future brother in law will work for the company too. As Jeongyun knows nothing, he end up feeling suspicious and jealous.
Start reading again at side 14.
Why Are You So Kind To Everyone Except Me?