Ran and Rindo

Everyone in this world has changed gender. Some retain their memories, some don't—mostly girls (or, more accurately, boys). Everyone's personality has changed, while others retain theirs. The Haitani also became the opposite sex, or rather, girls.

After the gender swap, Rindo became tactile, intrusive, etc. And Ran became pretty much the same. (They used to be like that too, but now they show it openly.)