Rick(MC) has been getting handjobs, oral, and anal from Rachel for several updates. In v0.12, Rick finds Steve and Emily on the island and brings them back to camp. A couple of days later, there is a scene on the island (not a flashback) where Steve is fucking Rachel.
There is a separate flashback scene in v0.12 where the MC is remembering how he saw Steve fucking a waitress in the bathroom of a restaurant while Rachel is waiting outside for Steve. This scene was mentioned in a previous update with a flashback, but now it's a full lewd scene.