awww what the ex (green-haired girl) said about moo-yi seems spot on. he's happy all on his own and makes everyone around him miserable. (poor young soo)
he never really opens up and brushe aside anything he thinks would worry the people around him. except they still do worry. i think he matches yoo-il in the way they both don't introspect on their issues, and don't pry on other people's circumstances as well. they both do their best at work, and they get inspiration from each other's work.
if they want to effectively go steady though, more than enjoying each other's companionship, they'd have to talk to each other. but right now, they've only just started opening up (that confession scene), they still have a looooonngggg way to go.