Silent and I have decided on the following: 

1. Jar and Yuki broke up roughly a month prior to the trip
2. They were together for about three months
3. Jar got drunk at a party and hooked up with a girl
4. She's heard Jar's friends names in passing but she has not meet them before nor has she seen pictures of them.

Also, Yuki has not told her friends about Jar and her breaking up so she didn't worry them.