Turns out Risa was going to go swimming with them. I didn’t think it would be a good arc without the four of them there.
Perhaps it’s the feeling of being left alone or behind, but you sometimes want to be with your friends. That seems to be Risa’s case here. Does she really have an air conditioner? Well, even if she did, it probably broke. I know my air conditioner broke, and it was nasty hot that day when I needed it. Hopefully Risa can cool off in the water.