In order to understand the world, one has to turn away from it on occasion."

The mirrored lines between Han Tae Sul and Kang Seo Hae are on point. Here are two that I found:

About connection:

KSH: "You're the only person I know whether from the past, present, or future"

HTS: "You're the only person I can trust whether from the past, present, or future"

About not letting the future self define them:

KSH: "You said that I'm going to fail,  but I'm still going to try. Because I haven't done anything yet"

 (KSH: Everyone will die because of you, even my mom--) HTS: I didn't do anything yet!

I would love to know about other ones I have missed

Tae Sul - I've always wanted to do this

*everyone watching dumbfoundedly thinking he is about to kiss her when a nuclear explosion is about to occur in 72 hours*

Tae Sul - *proceeds to quote Stephen Hawking*