I get that tbh
Other than it just being manhwa logic lol it's def a case of euihyun was able to rely on taeju and just that in its own made him feel safer than he ever has even with it starting as a "personal prostitute" scenario.
Re read the manhwa, there's a moment even for Euihyun not wanting to acknowledge his own feeling for taeju. It's fucked up reason bc Euihyun never feel attention of another person caring for him, so taeju bare minimum got into him, like the way he protected euiyoung, provide apartment for them, etc.
He got attached, that's why when Taeju selflessly run towards him near the beach, euihyun said inwardly "so you've gotten attached too"
For me, based on so many red flags i read, taeju is the rare species that tried to apologize vocally and admit his own mistake most red flags i know is just forceful even until the end, not saying sorry even for one time
this is rlly good but its just really predictable abt whats gonna happen, like its good but like there's no like heart tugging moments that make you feel bad for the seme and what he did to the uke bro that's just my take i just don't understand what made him suddenly want to be with him