Pikario

Pikario is a fairy who grew up on Mt. Ichigo and the younger twin brother of Kirarin, who he accompanied to France to study sweets. He is now one of Ichika's classmates. He likes making waffles and dreams of becoming one of the legendary pâtissiers known as Precure.

Personality
Pikario is very sensitive, both in being emotional and observant. He has a hard time confronting his problems, often trying to run from them, and he lacks confidence in his abilities as a pâtissier, especially when comparing himself to his sister. He is also fairly intelligent, curious, and clever. He seems to truly care about and enjoy spending time with people, though he acts rather distant and cold at times.

Pâtissier training
Pikario grew up happily on Mt. Ichigo, learning to make sweets with the other young fairies there and dreaming of becoming Precure together with his sister, Kirarin. One time when Kirarin was upset because her whisk broke, he made a waffle for her to cheer her up, and she told him it was the best waffle she had ever had, which he was happy to hear.

To further their learning, he and his sister set out to study in France together. While there, she grew more absorbed in her studies, and Pikario felt left behind by her. One day, she gained the ability to transform into a human, while he had been trying to make waffles for her again. When she tried the waffles, she said they weren't as good as the ones he had made for her before, which hurt him a great deal, especially as she was continuing to make more and more progress compared to him. After she left, oblivious to his pain, he ran off and ended up crying in an alley. In this alley, he was confronted by Noir, who said he saw his potential and offered him power, turning the kirakiral in his heart dark and transforming him into Julio.

The kirakiral thieves
Julio then went back to Japan and found some other fairies who wished for certain attributes, such as strength and beauty, and tricked them into accepting things that corrupted them by offering them the power to achieve these things.

After these fairies kept being stopped by the Cures, he brought them all together to attack the town's sweets festival. He mostly stayed back to watch, but once he noticed the Precure, he transformed them into a single stronger monster. He then watched as the Cures received kirakiral from the people of the town who wished to help them win, granting them more power, which they used to defeat the fairies and break the things he had given them. He then took note that kirakiral that had been in someone's heart shined brighter than when it was taken directly from sweets.

Kirakiral from the heart
After the sweets festival, Julio started attending the same school as Ichika, Himari, and Aoi, going by the name Kuroki Rio. He quickly became popular there, as the girls found him attractive and the guys thought he was nice, in addition to being skilled at several things. He was in Ichika's class, and he took an interest in her due to the kirakiral produced by her sweets. At one point, he was about to try to steal the kirakiral from her heart, but he was interrupted by Ichika's friend Risa, who asked him to join her for lunch.

Later, he accompanied Ichika and Risa after school to make a new cupcake recipe Ichika had come up with, though he declined to help, as he didn't really want to be involved with baking because it reminded him of his past, and, with the kirakiral in his heart being dark, anything he made would quickly be drained of its kirakiral. However, when Ichika was having a bit of trouble with the mixing, he gave her some advice on a better way to do it and was pleased when it seemed to work, though he seemed confused by his own enthusiasm.

After they were done, he asked Risa if she wanted to go ahead and have the cupcakes, and she decided to have just one. After this, he stole the kirakiral from her heart, causing her to let out a scream, which Ichika heard, rushing to the scene with the other Cures, though he had quickly transformed out of his disguise after stealing the kirakiral, so they didn't recognize him when they got there, and when he introduced himself as Julio, only Cure Macaron seemed to notice the similarities to Rio.

He used Noir Decoration to turn the kirakiral he had stolen from Risa into a sword, which he used to fight the Cures, referring to the whole thing as an experiment. He proved to be a formidable opponent, and when he was angered by Cure Whip's assertion that sweets should bring warmth and happiness and not be used for something like this, he launched an even more powerful attack, which Cure Whip then countered using the same technique that Rio had taught her earlier. Recognizing this, Julio put the pieces together and realized that Ichika was Cure Whip, and, by extension, he figured that the others at the KiraPâti were likely the other Cures.

The power of knowledge
Having overheard that Ichika, Himari, and Aoi would be helping the local grocer with PR, Rio approached the timid Himari to talk to her about it. He told her the Precure would be an easier way to accomplish things and told her she should just give up, possibly in an attempt to get her to do something that would help confirm his suspicions.

Later on, he watched as Himari managed to work up the courage to explain the science behind churros to a mother and daughter. Seeing the amount of kirakiral this produced in their hearts, Julio stole their kirakiral right in front of Himari, who was quickly joined by the others from the KiraPâti. When Himari demanded that he return it, he told her that if she really wanted it back, she'd have to take it from him. Upon hearing this, the five of them quickly transformed.

Julio then used Noir Decoration to turn the kirakiral he had stolen from the mother and daughter into a bow that seems able to produce an infinite number of arrows and could fire numerous at a time. He seemed to be doing fairly well until he angered Cure Custard by calling laughing and calling it an amusing experiment, when she ended up using a new move to destroy all the arrows he had launched at the time. Though he was defeated, he said that the experiment was a success.

Music's amplification
After overhearing that Aoi was forbidden by her substitute guardian, Mizushima, from continuing to play music and work at the KiraPâti, Rio told the others that he thought they should stay out of it, saying they could just make things worse and that one can never count on others to understand how they feel. He then waited to see how they would respond, becoming greatly confused when Ichika said she wanted to go back to Aoi's house to try to help Aoi get her feelings across to Mizushima, and was completely shocked when the others all agreed with her. As they all prepared to make sweets together, he left without a word.

The next day, he watched their plan as it was set into motion. As Aoi sang a song that reflected her feeling on everything, he was surprised to notice that the music amplified the kirakiral a great deal. He waited until the performance was over and Mizushima showed little sign of budging before beginning his new idea for an experiment, stealing the kirakiral of everyone present aside from the Cures. With the kirakiral he stole this time, his weapon bore resemblance to a triton, and he used it to launch an attack resembling icicles.

As they fought, he noticed some kirakiral that he seemed to have missed before, and tried to take it, only to be stopped by Cure Gelato, who noticed that the kirakiral was playing back the song she had sung. After they realized that the kirakiral was coming from Mizushima's heart, Gelato borrowed it for a bit and used it to launch a new attack against Julio, who seemed confused by the power she had received from it. He found it interesting how a single person's kirakiral could triumph over that of many.

Etymology
Pikario (ピカリオ) is based on certain Japanese words relating to sparkling, like ピカピカ (pikapika), which indicates something sparkly. It may also be based on the Japanese word for light, 光 (hikari), as sometimes (though rarely) it can be read as pikari.

Julio is a Spanish variant of Julius, although this is based more on the spelling of his Japanese name (ジュリオ) than the pronunciation, which is closer to the Italian version of the name, Giulio. Julius may be derived from Jupiter, which comes from Zeus, which derives from a word meaning "sky" or "shine".

The surname he chose for his alias, Kuroki (黒木), contains the kanji for "black" and "tree". The tree part may seem random, though he does seem awfully fond of sitting, napping, and just standing in trees.

The given name he chose for his alias, Rio (リオ), doesn't have a clear meaning and was likely just chosen to go along with Pikario and Julio.

Trivia

 * His voice actress Minagawa Junko also voiced Toyoshima Hidekazu in Smile Precure!.