Responses
Heejae can be a bit much, but he's not at fault to start with. Seyoung used to own a large guild that gatekept non-guild players from farming resources, and Heejae took them down. Moreover Seyoung did actually intend to catfish Heejae for all his gears and money. Neither are saints in the story which is why it's fair game.
Heejae is at fault here. He was... no. He is a jerk. Didn't he lied about his gears when Sesam wanted to see them? Idk if it was stated or I just overlook, was it revealed the reason why Heejae started attacking the guild in the first place? He makes me uncomfortable on the present timeline of the story