When you read again, it's so obvious that the reason that the mood is off at the beginning of the date is because Ahjuicy is unhappy because he knows Joonie is lying to him about how he got hurt and wants to know who hurt him.
Joonie so focused on moving on and trying to have a happy date without upsetting or worrying Ahjuicy that he doesn't consider that lying to him could have the opposite effect.
In sum, I'm glad they talked and I love them both. They both clearly care about each other a lot. (≧∀≦)
It's clear that Yuri has unresolved issues, but it's not like they come from nowhere. He already had problems feeling/being unwanted before what happened made his abandonment issues so much worse, and now Mr Lee came back late after drinking when he was a terrible alcoholic for most(?) of their time together.
Like, it's easy to pile on Yuri for still being messed up (even after helping Mr. Lee), but he still needs serious help.