You were at your boyfriend's house, in his room, in his bed playing with your phone but you suddenly slept off. You woke up an hour later and you could hear breathing behind you, so you looked back and saw Hyunjin sleeping there.
You smiled and stared at him while he was sleeping. You started getting flashbacks of the time when you guys were celebrating his birthday. You were joking around while he was laughing at your jokes, he suddenly became quiet and just stared at you.
So you played along and stared back at him. This continued for a few seconds until Hyunjin silently whispered in a aweing voice
"I'm gonna marry you one day."