you can say he's a user. The red haired guy is a user may it be a girl or a man who is rich. He will do it for the money i think. You said he had sex with a guy in hotel, yeah, because that guy is rich he is a business man, with a lot of chain stores. So the red haired guy eats whatever or whoever he can take advantage.
That's a good point since Taesung parents both knew they are a couple. So just in case this situation gonna blow up and will reported to the President which is Taesung's dad, he will surely fire the red head guy hahahahah(▰˘◡˘▰) I'm hoping. Let's just wait. Hope the red haired guy will be fired from the company.
Based on the RAWS lastest Chapter:
The red head guy is only using Haeboom since he suspected Taesung is in relationship with him. The red head guy is after Taesung!!! There was a flash back where the red head guy first met the two on their first day of work, that's when he saw Taesung wearing a high class or whatever expensive suit and shoes. That's why he's after Taesung because he knows he's rich. He needs money y'all. The red guy also set up Haeboom just to get scolded by the boss. WTF! You can see Haeboom crying on the stairs and Taesung was texting him if it's ok or what the hell happened. When Taesung is about to go to comfort Haeboom, the red haired guy just followed him. I'm angry as f***k!!!!
P.S. maybe the red head guy just suspected it so he wanted to confirm it. But we all know, he can think he already knows that the two is a thing in his mind. So he's working his ass off on the side. Remember, a whore or a homewrecker knows how to investigate and be observant. He knows what he is doing.(╯°Д °)╯╧╧ (/TДT)/
Another Spoiler:
http://www.mangago.zone/home/mangatopic/8665074/
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