I've decided to watch this drama due to interest in the teasers and I'm really loving it.
After watching a bunch of romcoms for a while, I find this kind of show really refreshing. It's so intense and the acting feels almost movie level of quality.
Alot of folks here seem confused but I actually find the drama quite easy to follow. 3 and 4 reveals more to the story. There are still some questions unanswered but I think that's intended.
Tae kyung was always going to become a lawyer. Since he was going to make more money from the job, he wanted his younger brother to quit his job, as a delivery truck driver, so that he can continue his education and tae kyung could pay for his schooling. However, Lee Tae Kyung's younger brother, the delivery driver, was killed. The ones involved in the murder got off lightly because their relatives are rich. Tae Kyung suspects wasn't an accident. So he then makes the deal with Woo Yong (Woo Yong offered it first) to work for him (as a lawyer) so he can pursuer revenge for his younger brother which resulted in Tae kyung murdering those who killed his brother. Woo Yong covers it up, so Tae Kyung can kill them without the consequences of jail/charges. But I think what led up to his brother being killed and the connections behind it is the mystery.
Anyhow, TaeKyung originally made the deal just for revenge but then he slowly became more corrupted and coldhearted from all the money and power he was receiving. Hence why he said in the 2nd episode that he was going to forget about his brother so he can take full advantage of the deal woo yong gave to him. In the latest episodes, Lee kyung is heavily suspecting a connection between his brothers death and Yang Chul GI, this clue brought his drive back to understand why his brother was killed.