If you haven't managed to piece together the puzzle, here are the spoilers:

- The rider is the man bleeding in the foreword as hinted in chapter 9.  

- Sunggyu, Dongwoo and Sungjong are contract killers who will do anything, kidnapping, killing etc.  Their next job was to kill Woohyun.  Sunggyu and Dongwoo are cops but they are also killers.  Sungjong is younger so he hangs with a group of teenagers who are the local troublemakers but he is also a killer.

- L is the leader of the gang that is terrorising the city.

- Sungyeol and Woohyun are not blood related.  

- Hoya was introduced in chapter 5.  

- In chapter 2, when Woohyun and Sunggyu first met outside the shop, Sunggyu has a baby with him.  It's not his baby.  As explained in the last chapter, Sunggyu along with Dongwoo and Sungjong kidnapped the baby for ransom.  So in chapter 7, Sunggyu wasn't lying when he said the baby went back to his mother.  She paid the ransom and got her child back.

- In chapter 3, the two masked people who attacked Woohyun is Dongwoo and Sungjong, while Sunggyu tries to get close to him.

- In chapter 9, the rider explains that when he was dying on the street, Woohyun gave him his jacket which kept him warm on that cold night until help arrived.  This was a hint if anyone picked up on it.

- In the final chapter, Sunggyu tells Woohyun to run but Woohyun doesn't.  He says that he's dying anyway because he has an illness and doesn't see the point in running.  Dongwoo intends to kill Woohyun but Sunggyu decides that he will do it instead.  Sunggyu stabs Woohyun and leaves him for dead.  Did he really kill Woohyun?  The hint was in what Dongwoo said to Sunggyu as they walked away and what the rider said to Woohyun when he found him at the end.  

- In the end, Woohyun finally sees the rider's face and it was someone he was not expecting, which means it can't be Sunggyu since he had always thought that it was him.

- So, if the rider is the bleeding man in the foreword, you need to find out why he was in that condition.  The rider wasn't a homeless man like Woohyun thought he was.  Woohyun didn't know the man was bleeding.  He was bleeding from the wound and waiting for help to arrive.  He didn't say the ambulance.  That's because help was his people and not the ambulance.

- And from all that, I hope you all figured out that the rider is L.  He is the leader of a gang, got wounded, waited for his people to come find him and has the power to find the boy who gave him his jacket.  The rider rang Hoya and asked him to help Sungyeol.  If L is the rider and has the power to order Hoya around, then Hoya has to be his bodyguard.

- Finally, will Woohyun accept L, knowing that he was the rider who had saved him several times?  Was Sunggyu such a cold hearted killer?  Did Sunggyu really love Woohyun?  I'll let you decide.

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Author's note:

Did we get all that?