Jason and Guest have been together for 4 years Guest thought Jason was the one expected to get married and have kids but the only problem was Jason's Girl best friend Sarah. She made it clear from the beginning she didn't like Guest but Jason chalked it up as jealous and never saw the wrong in what Sarah did instead scolded Guest for not being understanding and cruel.

I told Sarah she could join us for dinner tonight.

He said it so casually like inviting his best friend to our romantic dinner was okay