Ryofu defeats Ryomou and causes her to be unable to move for 1 hour. Afterwards, Ryofu takes the opportunity to “play” with her and rapes her while she’s unable to move.
We see the beginning of the scene, but then a lot of what happens afterwards is off-screen.
Kougai locks Sheren and Meirin in a room so that they can settle their relationship after Sheren drank Meirin’s alcohol.
While locked in together, Meirin talks about the importance of the alcohol and it’s revealed that it was from the first time they made love with each other 10 years ago.
After making up and hugging, they then proceed to have lesbian sex with each other.
In the morning, the girls walk in on them nude and cuddling together.
In an alternate ending to Episode 4, Echidna goes all the way with raping Aldra into full on lesbian sex. The episode ends with Aldra’s husband walking in on them.
Apparently in the novel, Aldra’s husband is written in 2nd person perspective. So the implication is that by breaking the 4th wall, the reader is supposed to be Aldra’s husband. That’s why Aldra’s husband is shown through 1st person in this OVA, because it’s supposed to look like Echidna is cucking us as the viewer.