Help!

Help! I'm looking for a webtoon about a man (the protagonist) who works in construction but is studying to join a company. He eventually gets into the company, and a whole situation unfolds: it turns out the owner of the company is the protagonist's biological grandfather. Years ago, the owner's adopted son killed the protagonist's father and had been constantly forging the DNA reports.
The protagonist didn't know the owner was his grandfather and actually thought the man had a romantic interest in him —it was a funny misunderstanding. I got to the point where he found out he was his grandfather, but all the mangas I had in my 'reading' list disappeared and I can't remember the name! Help!!