I don’t remember Hajin wanting to seek justice in Taekang. Both his original group and Taekang seemed to be in the same businesses. When he was still Hajin he wanted to take over Taekang, basically dismantle it and absorb them into their group.
In the background search for Sihyeon, there hadn’t been anything about Taekang being involved in Sihyeon’s life. Sihyeon did owe money to Jujin group though.
Now Daejun is coming back and telling him not to get involved with Taekang, why? I don’t know. The only involvement between “Sihyeon” and Taekang would be the info that “Sihyeon” mysteriously has. Hajin doesn’t know that Daejun knows that he’s in Sihyeons body, so whether the warning was for Hajin in Sihyeon’s body (search for Taekang info for Daejun) or because of the original Sihyeon, idk.
It’s so confusing
Ch 15: So Taekang was a small enemy group (loan shark/gang) who’s info Sihyeon was trying to trade Daejun in exchange for info on “himself” (Sihyeon).
When he was still in his original body (Hajin) he had info on Taekang and was thinking of absorbing that group into their group.
I don’t know why Daejun would be warning him about Taekang when no one (Daejun excluded) knows Hajin is inside Sihyeons body and Sihyeon “shouldn’t” have any connection with them.