If you're talking about the end part it's probably talking about Sejun. Because he's going down this bloodthirsty path of revenge like jason used to be or something like that. So Jason is like thinking about how he achieved his revenge, dwindled into a lifeless husk because there was nothing left for him, until he met the gym family ofc. And what Jason wants is to help Sejun achieve HIS revenge so that the kids can go back to a peaceful life of happiness. So yes ofc Hajin is a huge motivator, but in this instance Jason is thinking about Sejun.