
Seo-in after learning yeonwoon gets abused by his dad, immediately tries to help yeonwoon and even offer him a place, tried to kill Taegu first time meeting him cuz he thought (he's right) that taegu is the cause for yeonwoon's suffering from debt.
Vs.
Taegu, sure he made sure that yeonwoon's dad's debt somehow slightly manageable, that still didn't change the abuse yeonwoon got frequently, you'd think he couldn't stand the years of abuse especially when he watched yeonwoon grow up, he doesnt stand by it but he can tolerate it, because its his job, he could have still offered a place to stay for yeonwoo but he doesn't.
Now he looks at yeonwoon at a different way, iykwim