What are the main characters trying to achieve there? That lot tried to rape one of them, yet now they are just chatting all happily, as if they belong there. I seem to recall they were supposed to travel to Tokyo to see if the lab is still usable, to make more vaccination. But now they are playing games with this criminal bunch. It has only been a month, with most people going full zombie, so there's no end of food available, especially if they leave that hideout and look for better places. This is nothing but waste of time for no purpose, trying to help rapists. The sensei only stepped forth because the security team was losing the fight, so he had to pretend those goons were acting on their own. Otherwise he wouldn't have given a damn about the goons raping an outsider. In fact he was right there when Kanae was separated from the rest, because he was the one who gave the order to split the trio! It was that sensei who left Kanae alone with the goons.
You can be fooled once and not feel bad about it, but if the same people fool you twice, it's your own bloody mistake.