S. Korean Conscription is mandatory for men over 18, and last 21 months- in the army (23-24 months for the navy and airforce) That's basically two years. Yoon bum mentions that he first encountered Sangwoo in his first year of college and conscripted 4 months after 1st semester. Assuming Sangwoo graduated high school, and entered college immediately after (18-19 age), Sangwoo literally had to have conscripted around the same time Yoon did to.
If he did, Sangwoo has made no indication that he re-entered to college, or any indication at the beginning of the story that he recognized Yoon Bum even though they should have finished around the same time give or take a few month (if he entered at 19- he'd still be in the military right now [assuming he didn't lie about his age]).
I also want to point out how in the initial flashback- 'Sangwoo' doesn't even look like the Sangwoo we're familiar with (like a buzz cut?), the only indication we have is that they have bags under their eyes in profile. Yoon does not see Sangwoo's face very clearly when he get's saved, or even when he tries to get his attention the first time- indeed the military guy just kinda shrugs it off like there's no recognition. Initially, I thought it just meant that Yoon was not the noticeable sort that people like Sangwoo paid attention to. But Sangwoo has repeatedly expressed mockery and disgust for homosexual tendencies, and no indication for enthusiasm for conscription- so why would he even sign up in his first year of college? much less stop a rape attempt on a 'weak' stranger. He's not the type to do right by a stranger- that's more like Officer Seungbae than Sangwoo. Whatever 'Sangwoo' Yoon constructed does not exist-and probably never has- because the person who helped him couldn't have been the real Sangwoo- not without contradicting his characterization.
- Jossed◊ by artist/author on their twitter account; the military guy is indeed Sangwoo.
- Jossed, none of these happen.
Yes, it seems he got run over in the end, but we never see an actual car coming or if there is one I believe Seungbae saved him either from being hit or after being struck. Apparently, the Author once answered the question whether Bum died or not on her Twitter, saying that he didn't die.