Her real name is Reina.
"Reina decided she wanted to start a new life in Hinamizawa. She couldn’t stand the name Reina anymore… It brought too many bad memories (iyana koto いやなこと). So she took out the ‘i’ from her name.Rena didn’t want to be a bother in her house. She felt she shouldn’t be there when Rina was around. So she looked around for something to pass the time with. That became her Treasure Hunt. She finds an old car and makes her secrete place there. For some reason the electricity is still alive at the Dam Construction office so she connects several extension cords to power the lamp she finds and keeps in her car. Here she can find her escape. Here Rena can remind herself that she is happy, to not to think that she’s unfortunate. Satoko-chan and Rika-chan had it worse. They both lost their parents. She still has family. By staying perspective she can protect herself from the bad guys because it was she who allow the misery to fall on her. By saying the magic word Hau~ she can be happy again. She’s already taken out all the bad memories with her ‘i.’ She can become happy again. With all the bad memories (iyna koto いやなこと) gone, all that remains are the good things… ah… then she realizes the good things also being with ‘i’ (ii koto いいこと)…" - The game