The kids are playing with a box of old toys they got from Pops, in front of Saito for some reason, and Saito digs into it and starts playing with a spinning top. The girls don't understand the point of these toys and they're like "I wonder if Pops is trying to tell us he didn't have fun as a kid."
Then they read a picture book about a zoo that killed all of their animals with poison, except for the elephants which could smell the poison so they had to kill them by not feeding them instead... they all cried from reading this, including Kotoha who was trying to hide it... and then decided to go to the zoo in order to help out so that they won't run out of money and need to kill all the animals... except they got in for free because they're kids, and they paid to go on the monorail which is a separate service that doesn't go towards the zoo's profits...
lol I like this part where they are trying to get some bird's attention, and they're acting really silly, and the bird isn't reacting at all.
Then they go to see some mice, and after learning that they multiply very quickly, they come up with a conspiracy theory about how these mice are being used to feed all the other animals and that's how they can afford to let kids in for free. They don't believe the staff worker who says that's not true, because he looks like Saito.
Sat-chan pointed out that she saw an animal pooping... and Yui commented that it's unusual that this is the only time she's mentioned poop so far today.