Volume starts with the class president escaping with the bottles of water. The president escaped because he was caught by the delinquent attempting to rape the blonde girl classmate. The delinquent student also discovered that the cave they are in was a corpse-dump of the natives so they opt to find a new place to stay. They soon found wreckage of ships and the blonde girl classmate chose to explore one ship wreckage (which I think is a lifeboat) to find some supplies. She found two corpses in a hugging position and the diary that belonged to the corpses with an ax. Inside it is a picture of the corpses. She returned with an ax which she bought along to the shore and encountered the shark along the way. She was later saved by the deliquent by pulling her out of the water. Later they sent out to find food or supplies that was written as instructions in the diary (there are also some notes in the diary but I can't read it since my Nihongo isn't that good). While exploring, they stumbled on the half-dead body of the president (I think---he's face is different from the beginning of the volume so I can't tell if it's really him).
Meanwhile, FMC was presented to the alpha male native along with his harem/sex slaves. Intercourse happened through out the night but FMC didn't join the act and was spared by the alpha native. On MC's side, he's on the middle of a mission to rescue FMC.
Most of the volume was focused on the group of student's survival. Next volume, we'll know what happened to the corpse as well other student's situation.