
Owww shit. Heeseo and the criminal mom was in the same place same time as when Taekyung and the old guy criminal/witness had a face off???? Like what the hell off all the abandoned buildings in korea @.@??? So now it's obviously the criminal mom who killed the witness and was probably trying to kill taekyung/heeseo too so heeseo kinda escaped and took TK to protect him @.@

What I read from previous spoilers
Soohan wanted to KMS because he got SA-d that time by the cousin (who's coming to take over his position at the company now) and it was kinda indirectly the kids fault because he wouldn't have been in that cousin's radar if the kid wasn't so clingy to him. It's also partly his jealously and inferiority complex like "this kid is living the life while I suffer so much" that he kinda tried to strangle the kid.

Sorry but the TL is totally wrong..
SH tried to KMS and strangle YS when he was in middle school.. he wasn't in the best place mentally, you'll understand once SH's past before he came to live with YS and his family is revealed.. SH was suffering..
After that he got into high school and went to the dorm.. later he went to study in France for college..
the SA happened when he came to visit while in college bc YS was about to enroll in college in US.. when SH was sleeping with his sleeping mask on he was in heat and YS's cousin who was in the house looked down on SH whom his parents praised over him.. so the cousin decided he would "teach a lesson" to SH.. he tried to force himself onto SH but SH smashed a lamp and stabbed the guy with a piece of glass.. he did not reported the incident bc he was worried he might get sued for excessive self defense.. however since SH was about to meet the family in their beach house he thought YS was the one who assaulted him..
SH knew YS liked him and he also knew the parents kept him around as a "future bride" after he turned out to be an omega.. he thought the parents covered it up and acted like nothing happened to protect SH.. so he was resentful of YS.. the accident happened when he was about to go get evidence about who assaulted him..
SH is actually scared of YS who has everything loving him who has nothing in a way..
SH has quite a lot of issues and this story is his journey of overcoming them..

Before the accident, he didn't "know" it. He initially didn't give much thought to the incident. But then he started suspecting it, he didn't want to believe it wasn't YS bc that would mean he didn't have a valid reason to not accept YS. So to prove himself right he went to get the evidence and otw got into an accident..
After the accident, SH has not pre-concieved notions about anyone or anything. When SH gets kind of a flashback/dream about the incident after going into the same room he was assaulted in, he starts comtemplating who it was. He questions why would he not recognize YS's pheromones if they lived together after getting married but he realizes YS takes suppressants to not have his pheromones leak. But he ends up ruling out YS after probing him a bit and realizing his body does not react badly to YS's pheromones. He then starts suspecting the cousin bc he feels averse when he comes near him. But he is not sure if its bc its a trauma response or simply bc he does not like the cousin. He kind of becomes sure when he realizes just like he himself started taking suppressants to make sure his pheromones never leak out bc he was traumatized by the incident soon after it happened, the cousin too started taking suppressants to the point none of his pheromones leak out. He also remebers the first time they met at the company after he joined and the cousin was tense while asking "have we met before?" And he relaxed when SH replied that it was their first meeting..
I thought I was a crybaby to cry over a minor character but that was just so sad...