Due to Okabe's intervention in the form of a message sent into the past to Ruka's mother, Ruka experiences being a girl until he decided to return to being a boy after witnessing the consequences of her wish of being a girl. Rukako was his name during his time as a girl.
In this world line, Okabe decides not to send the D-mail that would make Ruka return to being a boy again. He convinces himself that Mayuri will still die no matter what he does and he doesn't want to sacrifice Rukako's happiness. The timeline goes on and Mayuri still dies. Realizing the devastation she has wrought, Ruka feels guilty about Mayuris death. Remembering that Mayuri wanted Rukako to cosplay in the next convention, Rukako with the help of Okabe, travels in time to give Mayuri at least some happiness. The plan is a success, as in that timeline Rukako, Mayuri and Okabe go to the convention together but Mayuri still dies. However, Okabe is okay with it, glad that he could give Mayuri some happiness.