The only times I've seen him look somewhat comfortable was when Han Ji-min was also there like Pinggyego & Whenever Possible, and the most comfortable I've seen him was the Marie Claire where he and Ji-min were asking questions to each other.

MBC dropped a second preview for #WhenThePhoneRings! Subbed by shengjianbaozis on Twitter video-s.twimg.com/amplify_vide...

#WhenThePhoneRingsEp5 prediction 2: he'll find out later in the ep it's Hee-joo but won't confront her about it and will continue the phone calls because he realizes it's the only way (for now) for them to communicate more honestly. Let's see if I'm right!