@Delilah And if you want to know more about what happens next too, even if I'm not sure it'll be in the manhwa (or as side stories!) :
Spoiler!
In one story, they're in Korea, they live together. Sang Woo's still a student, Jae Young's working (having made a strong impression on his colleagues).
They have organized a lot to live together and Sang Woo imposes a lot of absurd rules that exhaust Jae Young quite a bit. Indeed, he's trouble seeing everything Jae Young does for him (he prepares breakfast for him every morning, for example, but he only sees the dishes that Jae Young didn't have time to do because of his exhausting schedule). Sang Woo doesn't want them to have s** on weekdays, he doesn't want them to sleep together in the same bedroom, he makes carrot juice to help Jae Young with his eyes (who's had his vision reduced since he works), but Jae Young doesn't drink it because it's horrible taste... In short, a lot of criticism comes from Sang Woo's side, with Jae Young who accepts and says nothing, compromise after compromise while it is Sang Woo who is persuaded to pile it up.
They have organized a lot to live together and Sang Woo imposes a lot of absurd rules that exhaust Jae Young quite a bit. Indeed, he's trouble seeing everything Jae Young does for him (he prepares breakfast for him every morning, for example, but he only sees the dishes that Jae Young didn't have time to do because of his exhausting schedule). Sang Woo doesn't want them to have s** on weekdays, he doesn't want them to sleep together in the same bedroom, he makes carrot juice to help Jae Young with his eyes (who's had his vision reduced since he works), but Jae Young doesn't drink it because it's horrible taste... In short, a lot of criticism comes from Sang Woo's side, with Jae Young who accepts and says nothing, compromise after compromise while it is Sang Woo who is persuaded to pile it up.
At one point they're in the car, Jae Young wants to do it there, but Sang Woo's a rule to only do it in the bedroom, so he breaks the mood a bit and frustrates Jae-Young.
But here, another element that Sang Woo wants to change is the way of writing sms of Jae-Young. He writes without space, which complicates the reading and makes it somewhat difficult to understand and tiring to decipher. So he wants Jae-Young to fix that because he makes "mistakes". He constantly tells him to be careful with his spelling.