Hibari has a tragic backstory throughout the series along with her long-time rival, Mirai. She comes from a long standing noble ninja family that has spanned generations. Even her immediate family is pretty large, as she has a huge amount of siblings.
Despite all of her brothers and sister having far more skill and promise as shinobi, Hibari was the one chosen to be the heir to the family. This was because she was the only one to develop the family's signature power, Kagan.
Hibari never really wanted to become a shinobi. She wanted to open a shop and sell sweets. Despite showing questionable potential as a ninja and messing up quite often, her family was always positive and supportive of her.
Instead of showing resentment of jealously, her siblings would instead be proud and encouraging, which Hibari found to be odd and even discouraging, given her ineptitude.
However, with the degree of enthusiasm and support from her family, Hibari couldn't bring herself not to follow through, now doing her utmost best to become a great shinobi. This is probably where she gets her innocence and sweetness from, but is also the source of her lack of confidence in her own abilities.
Something is very dark about her, however, according to Yagyu, Hibari resembles her deceased younger sister named "Nozomi", who died in a car accident.
Hibari was in the ninja room when she noticed a flyer announcing the Super Dish Gourmet Cook-off. Normally she'd enter this kind of competition in a heart beat but decided against it as she'd put on a few pounds recently. She mentions to herself she loves food but it all went to her gut. She had a tear in her eye as she prepared to toss the flyer away until she spotted a few words that mentioned that there would be plenty of special sweets. She was surprised at this for a moment before whispering to herself "Sweets don't go straight to my gut." She whispers this to her heart before shouting out. "I've got a second stomach for sweets!" She screamed it out for good measure and she began to feel like she did have a second stomach that led to another dimension that didn't pack on the pounds, she says to herself she can do it before heading out. She then wonders what kind of sweets they would have.
Her first opponent much to her surprise is her teammate Yagyū. Hibari even questions her as to why she was there. Yagyū says that she did enter and asks her if she intended to eat while she was there. Hibari asks her what she meant and she was just there to cook and as she points out it was called a cook-off so she was just there to cook. Yagyū flat out tells her, she came to eat. Hibari begins to break down and tells Yagyū she was being mean and asks her if she was saying she didn't believe her. Yagyū tells her it was clear she had been eating too much recently, at this rate her body was bound to suffer and that's why she was here, to stop her. Hibari then tells her, she didn't come to eat maybe a little taste but nothing else. Hibari then tells Yagyū she can be so mean sometimes. And so the two face each other in the cooking competition with Hibari winning. Yagyū asks Hibari to listen and tells her to be careful to not eat too much. Hibari tells her she got it and it was just a couple of bites and proceeds to stuff her mouth with food. Seeing this Yagyū tells her to look at herself she was already gorging. Hibari points out that they can't let all this food go to waste so she kind of had to eat it and continues to do so. Yagyū tells her that was a slippery slope. Hibari tells her that slippery or not she had to keep moving forward as that was what they do as shinobi.
Her next opponent was Mirai who upon noticing her tells Hibari to take her best shot and eats some of the sweets. Hibari shocked at this asks her if she was eating before the match. Mirai says to her there was no rule saying they couldn't. Hibari realizes she was right and says to her now she had her eating too and eats some of the sweets. Mirai then tells her she couldn't resist either. Hibari tells her, she had it all wrong this wasn't her, her hands were moving on their own and tries to lie that Haruka was using her puppetry on her. Mirai calls out on the lie as Haruka wasn't there, she had returned to the hideout. Hibari mutters to herself that Mirai saw through it and shrugs it off as there was nothing she could do and eats more sweets. Mirai noticing all the sweets Hibari was eating asks her where she was putting it all. Hibari while her mouth was stuffed tells her she wasn't going to lose to her. Mirai in response tells her not to eat with her mouth full and asks where her manners were, at this point Mirai decides to get on with the match and tells Hibari to taste her unbeatable cooking. Hibari tells her she'd love to have a bite. Mirai asks her if she was still going to eat some more. And thus the two face each other with Hibari beating Mirai. After winning Hibari tries some of Mirai's food and tells her it was good. Mirai thanks her and asks her how her stomach was holding up. Hibari doesn't give off much of an answer and Mirai says she guessed that was okay. Mirai then continues about how Hibari was making her food look really good even her plates looked happier that Hibari was eating off them. Hibari with her mouth full responds and Mirai tells her to not eat with her mouth full.
Her final opponent was Yomi. While the two were eating Yomi tells her she finally came. Hibari upon noticing Yomi is told by her that the time has come for them to find out who was the bigger eater. Hibari tells her she won't lose. Yomi says to her that the rules of the contest demand a cooking battle. Hibari tells her she won't lose that either she loves to cook food and eat it. Yomi tells her that was the spirit. No diets, no modesty and no holding back. Hibari then says that she always had a second stomach for sweets. Yomi then tells her that her main dish qualifies as a sweet. Hibari then tells Yomi here she comes and Yomi says to her have at you before changing the last words to have a taste. And thus the final round of the competition begins with Hibari emerging victorious.
Upon winning the final match Hibari cheers over her victory only to see much to her and Yomi's shock the whole room was flooded with sweets. Hibari then comments that she seems to have made too many sweets and asks Yomi for any ideas on how to deal with it all. Yomi then tells her there was no sense in leaving leftovers for one thing. Hibari was in complete agreement as it would be a total waste. Yomi then says they had no other choice as she took it, and if it had to be that way. Hibari tells her it does and to do it. And so the two being devouring the sweets. While she was eating the sweets Hibari mentions they were the best she's ever made, they were so good she couldn't stop eating. Hibari says to Yomi they were so yummy. Yomi responds that they were perfect for a second stomach and they could eat all they want. Hibari then says they should stuff their faces. The sweet flavor spreads through Hibari's mouth she felt like her cheeks were about to melt, this was the greatest happiness in the world. At this point Hanzō speaks up saying he was done and falls over. Hibari asks him if he was alright she tries to wake him as there was still a lot of sweets left she gives up after calling out to him several times. Hibari then asks Yomi about plan B. Yomi says if that's what it took. The two glanced at each other and nodded. They then began eating more sweets. Hibari began to imagine she and Yomi were on a sea of sweets, together they swam through that sea, they just eat and eat and eat. Yomi then comments that she felt like she was in heaven which Hibari agreed with.