Reina was born in Hinimizawa and spent a great portion of her childhood there until they had to move. They moved because her mother (who like her father) was a fashion designer. Nut Reina's mother got a very great offer at a large company and her father did not. Infact, his luck with getting jobs was terrible. So he quite his job and became a house father, to take care of his little Reina.

As the days pasted, Reina's mother's success grew. She often came home late and almost never spent time with the family. She would, however, take Reina out once in a while and buy anything for her. On one such outing the mother brings a man name Akihito with her introducing him as her colleague. A few months later, the mother takes Reina out to an expensive cafe. Reina's childhood dream was to eat as much ice cream as she can and the mother wanted to fulfill that dream. While in her dreamland, the mother asks Reina whether who she likes better: Mommy or Daddy. Reina promptly answers Mommy as she thought it would be rude otherwise because of the treat she was getting. The mother then reveals that she plans to divorce her husband and remarry Akihito. Reina is, of course, crushed and asks why can't Daddy remain as family. The mother responds that she is pregnant with Akihito's baby. Later, the mother's lawyer talked to the father concerning the divorce. Reina is not sure if her father was warned beforehand, but she suspects her mother of never telling him.

Reina believes her mother and Akihito are her enemies because both are/were trying to destroy Reina's family. Reina's mother asks her to move in with her but Reian has already made her revalation. So, after realizing this Reina snaps at her mother and says, "Never show yourself in front of me again, and don't ever affectionately call me Reina again." Those were her last words towards her mother.

Reina relaizes because the Ryuuguu family abandoned Hinamizawa, this divine punishment came down upon them. So, Reina decides that going back to Hinimizawa (after being prescribed to drugs - because of her anger towards her mother (Via burning things)) is the right then to do. And so they move back to Hinimizawa in her grandmothers old house.

Reina decides that because they are starting life anew that she should change her name, mostly because it brought up so many terrible memories. So she takes away the 'i' in her name and she becomes Rena.

Even after returning to Hinamizawa, the father was still struck in deep depression. He had a lot of reprisal money from the divorce and never went to seek a job. He meets the show girl Rina who brought back his smile. Rena couldn’t say much about their relationship, because no matter how much she tried, she couldn’t bring back the same smile Rina did on to his face. As the weeks pass, Rena started noticing toiletry and other personal items that where not her or her father’s around the house.

So, Rena decides she needs to get out of the way at her house. She finds her own haven at the garabge dump.