This is a loaded question lol. Basically Lee Jung Woo is the main character of the Tong series. The Tong, Dokgo, and Blood Rain series exist in the same universe. Because they all exist in the same universe, you can see cameos of Lee Jung Woo and Hyuk (plus other characters) in the each other's series. For example, in ch. 58 of Dokgo, you see Lee Jung Woo asking Kim Jong Il for directions.
I was wondering about the timeline when I first began too, so I made a timeline of when the each season of all three series take place. It's not exact (i.e. for example, the events in Dokgo 2 happens a few months before Tong (season 3) begins), but it's close. Hyuk is two years older than Lee Jung Woo so the ages indicated in the timeline are referring to theirs:
------------------------------------Tong Memories (manhwa)------------------------------------------------------(15) Tong Memories (drama) --> Dokgo Rewind (17)-----------------
-----------------------------(17) Tong (season 1) --> Dokgo (season 1) (19)--------------
-----------------------------(19) Tong (season 2) --> Dokgo (season 2) (21)--------------
-----------------------------(19) Tong (season 3) --> Dokgo (season 3) (21)--------------
-----------------------------------(22) Blood Rain (season 1) (24)----------------------------
-----------------------------------(23) Blood Rain (season 2) (25)----------------------------
-----------------------------------------Blood Rain (season 3)----------------------------------
Blood Rain is the sequel to both the Dokgo and Tong series where characters from both are "officially" interacting with each other. It seems as though the fight between Lee Jung Woo and Hyuk is being set up. It almost seems fated because they're both legends and they also know a lot of the same people, however, they've never met each other before. Nonetheless, the meeting and fight will probably happen in Blood Rain (season 3). (Blood Rain (season 2) is currently being published.)
Forgot to say: I put Tong Memories (manhwa) first because it seems like it begins with Lee Jung Woo being in middle school and then going to high school. The Tong Memories (drama) goes into why he transferred to Seoul. There's also Dokgo Rewind (drama) which just recounts the events in Dokgo Rewind (manhwa), but not everything is how it happened in the manhwa (you know how it is when a book is adapted into a movie: things gets left out and/or changed because of the time restraints).
You can read them in whatever order because they were made out of order as well. Dokgo (season 3) hasn't been made yet even though all three seasons of Tong have been made. The order that I read them in is: Dokgo --> Dokgo Rewind --> Blood Rain (season 1) --> Tong series. My advice is to start with Dokgo first only because you're not introduced to too many (prominent) characters at once.
Blood Rain (season 2) is centered around Lee Jung Woo and Kim Jong Il. Kim Jong Il is one of Hyuk's best friends; he's the one who defeats people using pens. There's a bunch of other characters too this season: new Chinese gang members, Kim In Bum, Jung Woo's classmates and gang members, etc. The main focus should be on Jung Woo and Jong Il though.
Who is lee jung woo?did he appear in dokgo.,.im suck remembering korean names.,.hahahahha,what will i read first,tong or bloodrain?!.can someone plz tell me ,.tNx