"HAPPY 25TH BIRTHDAY YOONYUL!!!" Everyone wished the twins. It was the fifth day of the twelfth month and they had just reached another village, found a restaurant and bought a cake for the two birthday girls. The twins were delighted and after thanking the rest, they made a wish and blew out the candles.

Their beloved baby sister then helped them remove the candles from the cake, however, just as they were about to cut the cake, Seohyun smiled sweetly at them and smashed the cake into Yuri's face, before taking another cake that Yonghwa had kept hidden and smashed it into Yoona's face. "SURPRISE!!! Happy Birthday Unnis!!!" Seohyun shouted cheerfully and hugged both her sisters.

Looking at their cute baby sister, they could not bear to get angry at her but they decided to let her have a taste of her own medicine. "Gotcha!!!" Yuri whispered as she held Seohyun tightly in a backhug, while Yoona took both cakes and attempted to smash them into Seohyun's face.

"YONGHWA!!! SAVE ME!!!" Seohyun yelled and immediately Yonghwa stepped in front of her and had the cakes smashed into his face in place of his girlfriend. "Thanks Yong! You're the best!" Seohyun whispered, giving Yonghwa a peck on the cheek, some cream for his cheek at the same time.

"And that's two perfectly delicious cakes wasted..." Sooyoung complained. Hyoyeon shook her head in exasperation. "Oh well... LET'S GET THE PARTY STARTED!!!" Sooyoung shouted and rushed off to check out the buffet table for the party. "The food had better be good! I spent a lot of money to book the entire restaurant for their birthday party..." Sooyoung thought.

Leaning against a wall, Yuri surveyed her surroundings. First, she saw Sooyoung and Yoona having their own eating competition, with Hyoyeon as the judge. She smiled to herself as she thought: "Ah... The two shikshins are at it again..."

Looking away from the trio, she saw Sunny putting something shiny onto Taeyeon's ring finger and by the looks of it, both of them were blushing. "So now all the couples have couple rings..." Yuri thought as she looked down at her ring finger where she wore the couple ring that she had bought for Yoona and herself many years ago. Neither of them ever took it off, except when bathing.

Out of the corner of her eye, Yuri spotted the YongSeo couple chatting happily and feeding each other sweet potatoes. However, she could not see the JeTi couple anywhere. "Wonder where those two went... Ah, there they are! OMO, what are they doing?!!" Yuri thought as she spotted Jessica and Tiffany hiding in a dark corner of the restaurant, kissing like there's no tomorrow. Thankfully, they were still fully clothed...

Ignoring the kissing couple, Yuri turned her attention back to the love of her life and started to reminisce the past twenty-five years that they had spent together...

While humans only start having memories of anything when they are about three or four years old, angels and demons can remember everything once they are born. Naturally, Yuri remembered the scene that occurred when her twin sister and her first opened their eyes to the world...

[Flashback]

Twenty-five years ago, when YoonYul just entered the world...

"She's a demon!" God of Sleep exclaimed when his firstborn was delivered. The smile on his face grew wider when his firstborn's twin came out as well. "She's an angel!!! Isn't she a beauty!" God of Sleep added on. "Let's name them Yuri, Demon of Nightmares and Yoona, Angel of Dreams!" God of Sleep told his wife, who nodded happily caressing the soft cheeks of her newborns.

"I must be a mistake... Look at how happy dad was when Yoona came out... He was happy when I did, but he was sooo much happier when Yoona did... No one likes demons..." Yuri thought to herself as she curled up into a ball in her mother's warm arms.

Since they were born, the twins had a special connection between them which allowed them to know what the other twin was thinking. That was how Yoona knew how Yuri was feeling and immediately slipped her arms around her elder twin and gave her a tight hug, whispering: "It's okay! You still have me and I will always think you're the BEST twin ever!!!"

Yuri felt much better after hearing her younger twin's words and feeling the warmth of her twin against her back. Turning around, she saw her twins angelic smile and she smiled too. Sparks flew and from that moment onwards, the twins were inseparable and later on they found out that they had already fallen in love with each other since then.

At that moment however, all they knew was that all they needed was each other and with slight giggles from the twins, they embraced. Black light engulfed Yuri, white light engulfed Yoona, as they instinctively revealed their weapons forms as all weapons do minutes after they were born.

Yuri was a black sword, hilt decorated with the blackest of pearls, blade made of the purest black pearls around and with a small inscription in white along the blade that stated: 'Blade of Eternal Pain'. Yoona, on the other hand, was a white sword, hilt decorated with the clearest of diamonds, blade made of the whitest of marble and with a similar small inscription in black along the blade that stated: 'Blade of Eternal Bliss'. On the hilts of both swords were the inscriptions: 'Twin Blades of Eternal Slumber' indicating the two weapons were a pair and they would have the same destined user.

Yoona was perfectly happy with her weapon name, but although Yuri tried to pretend that she was happy with hers, Yoona knew that Yuri did not. Yuri was not happy as she did not like causing pain to others, she would gladly be in pain for others, but as weapon, she assumed that her powers would be causing immense pain to others, which she felt uncomfortable about. Once again, Yuri felt like she was mistake, her powers totally contradicting her personality, or so she thought.

At the age of three, the twins had grown up to two very cute and attractive little girls, but deep down they were downright mischievous and playful. Together with their then thirteen year old cousin, Sooyoung, they went around playing pranks on their parents, Soojin and their uncle. Their aunt was usually busy overseeing some battle somewhere, so she was safe from their pranks.

Once the two of them tried to prank Sooyoung and they succeeded, but they did not remain happy for long as Sooyoung hit them back fast and hard. They managed to retaliate of course, but soon it escalated to the point that all hell broke loose when Sooyoung decided to end it once and for all and summoned every single dead spirit and practically the entire demon army from hell to show the twins who's boss.

The twins fought back till they could not take it anymore and surrendered, admitting that Sooyoung was the best prankster of all times, but Sooyoung had to admit that her cousins were almost as good as her, for they had managed to fend off everything she threw at them, except for her personal bodyguard, who obviously would not lose to two three year old angel and demon.

At the end, the three of them decided to call a truce and Sooyoung and Yoona decided to have yet another eating competition with Yuri as the judge. Sooyoung always won, but Yoona never admitted defeat. Not sharing her sister's and cousin's love for food, Yuri once again wondered if she was a mistake...

At the age of five, they bade their dear cousins, Sooyoung and Soojin, goodbye as she left to join the previous Vanguard of Death. They missed them dearly, but that did not stop them from continuing to prank their parents. To Yuri, any time spent with Yoona were the best times of her life. She would protect Yoona with her life and she was willing to do anything so that Yoona would not be hurt. In short, if she could she would endure all the pain for Yoona.

At age eight, their baby sister Seohyun was born, immediately they knew that she was the one, their destined user. When Seohyun was born, Yuri thought: "She's sooo pretty and cute, just like Yoona... Unlike me... I guess I'm really a mistake... I think I'll nickname her SeoBaby! She'll always be my baby sister and I'll make sure she'll never have to experience any pain in her entire life."

Yoona squeezed her twin's hands as she leaned over and whispered into Yuri's ears: "You're pretty and cute too! And you're definitely not a mistake! SeoBaby is a nice nickname and I'm sure we'll do a good job in taking care of her together."

Yuri turned to look at her smiling twin, which cause her to smile as well before she replied: "Aish... Why to I always think of such unhappy thoughts at happy moments. Silly me! And of course we'll take good care of our younger sister!"

At age ten, their parents decided to go on a honeymoon and left the two year old Seohyun in their care. Yuri and Yoona treated Seohyun as their precious baby sister and they spoilt her, gave in to all her wants and made sure she was never hurt. Nevertheless, Seohyun grew up to be a sensible girl, who was not demanding and very understanding, with a huge craving for sweet potatoes, but that's another story...

As the twins grew into their teens, Yuri started to realise that she was not a mistake after all, for her actual powers were to prevent her user from feeling any pain and transmitting the pain back to those who try to harm her user. From then onwards, she became much happier and the three of them led a simple life, participating at duels in the nearby arena to get some money for their daily expenses.

Needless to say, all three grew up into very pretty young ladies, but Yoona attracted more attention than her, for everyone was scared once she revealed her true form to them. Even Seohyun attracted more attention than her, although that made Seohyun slightly uncomfortable. This resulted in Yuri wondering if she was really a mistake or not again.

Fortunately, she had two caring sisters who assured her that she had nothing to worry about and when Sooyoung returned with the invitation to join the Vanguard of Death, Yuri knew that their lives were going to get much more interesting. She looked forward to an exciting journey with her beloved sisters, vowing not to remain a mistake for the rest of her lives.

[End of Flashback]

"Yuuuuuuuuuuriiiiiiiiiiiii!!! Stop staring at me! How can I concentrate on eating, when the prettiest demon on earth is staring at me like that! You're going to make me lose to Sooyoung unni!" Yoona shouted across the room, bringing Yuri back to reality. Yuri smiled and walked over to the two shikshins, swiftly stealing Sooyoung's plate of food just before Sooyoung completed eating.

Running off speedily for her life she shouted: "Yoona! Quickly finish your food before I get caught! Sorry for distracting you!"

"YAH! YURI!!! COME BACK HERE WITH MY FOOD!!! NO CHEATING!!!" Sooyoung shouted, before she shadow jumped to Yuri's shadow and attempted to subdue Yuri and get her food back. To buy her twin more time, Yuri revealed her true form, her wings knocking Sooyoung off balance and she ran off again.

"THANKS YURI!!! You're the BEST TWIN I ever had!!!" Yoona shouted in reply as she gobbled down her food trying to make use of the time her twin has gained for her.

"I'm the ONLY twin you ever had!" Yuri shouted back, laughing as she tried to escape Sooyoung's grasp by teleporting around randomly. Finally, she got caught by Sooyoung just in front of the place where JeTi were 'having fun'. The two embarrassed girls blushed and instantly stopped kissing and groping each other. They were still fully clothed at that time, although how long more they would have stayed that way if there were no interruptions, is anyone's guess...

As they made some excuse to go to the toilet and ran off, Yoona exclaimed: "I'M DONE!!!"

"NOT FAIR!!! I WANT A REMATCH!!!" Sooyoung yelled back.

"BRING IT ON!!!" Yoona challenged and the two of them went back to the buffet table to pile their plates with more food for the rematch. Yuri shook her head, unable to comprehend how two skinny girls can eat so much and stay that size.

Looking around the room once more, she saw SunYeon and YongSeo both still engaged in conversations with their respective partners, seemingly oblivious of the scene that just occurred. Yuri then walked towards the toilet and thought with a smirk: "I wonder what JeTi is doing in the toilet..."