Regarding his relationship with the Slytherin students. They might be confused at first. The de - aged Snape could be more relatable to them, but also less authoritative. He might have to earn their respect all over again. At the same time, he could use this opportunity to change some of the Slytherin traditions or attitudes that he didn't like when he was older.
With his colleagues, like Dumbledore. When de - aged, Snape might be more open and less guarded. He may share his true feelings and thoughts more freely. Dumbledore might have to take on a more fatherly role towards him, guiding him through the challenges of being de - aged. And with the other Hogwarts professors, he could form new alliances or rivalries based on his new, younger self.
If Naruto gets de - aged, his friends would likely become very protective of him. For example, Sasuke might feel a stronger sense of responsibility to keep Naruto safe, since Naruto is now in a more vulnerable state. Sakura would probably mother him a bit, making sure he eats well and studies hard at the academy. His friends' perception of him would shift from seeing him as an equal or even a leader in some cases, to seeing him as someone who needs their care and guidance.
One plot idea could be that de - aged Snape has to adapt to the modern wizarding world in the community. He might be shocked by new spells and technologies. Another could be that he forms unexpected friendships with younger students as he is now closer to their age. For example, he could bond with a young Gryffindor over a shared love of potions in a new, more innocent way.
The relationship between Harry and Snape would change drastically. Normally, they had a very strained relationship in the original story. But with Snape deaged, Harry would see him more as a vulnerable being in need of help. He might feel a sense of protectiveness towards Snape, which is a complete turnaround from his previous feelings. As for Ginny, she would probably approach Snape with an open mind. Her relationship with Snape would be more of a nurturing one, like taking care of a lost child. And between Harry and Ginny, their relationship could be strengthened as they share this unique experience of looking after Snape.
He might become more arrogant. With royal status, he could develop a sense of superiority over others. For example, he might look down on his students more than he already does in the original story.
With Natasha, she might become more protective of Steve. In his de - aged state, she could see him as someone who needs more safeguarding, and their friendship could deepen as she shares her own experiences to help him adapt.
One possible fanfiction idea could be that Albus Severus Potter is accidentally de - aged by a misfired spell in Hogwarts. He then has to navigate the school as a much younger version of himself, causing all sorts of chaos and confusion. His friends and teachers are initially shocked but then have to figure out how to reverse the spell.
If he meets Lily in the afterlife, their relationship could become more of a true friendship. Without the complications of James Potter and the war, they could finally understand each other on a deeper level. Snape could let go of his unrequited love and instead cherish the bond of friendship that was always there beneath the surface.
His relationships can become more innocent. For example, with Hermione, she might be more protective of him as if he were a little brother. Instead of their usual intellectual banter, she could be guiding him more.
At first, Severus would be exasperated by Harry's mischievousness. He might deduct points from an imaginary house just like he does in Hogwarts. But then, he'd remember that Harry is just a child and doesn't fully understand the consequences. He could then try to use positive reinforcement. For example, if Harry behaves well for a certain amount of time, he gets to learn a new spell or potion ingredient. This way, Severus can gradually shape Harry's behavior while also building a closer relationship with him.
In romantic relationships in fanfiction, Snape can be quite badass. He might be very guarded at first, not easily giving in to his feelings. But when he does, he's all in. He'll protect his love interest from any danger, whether it's from dark wizards or from the prying eyes and gossiping tongues of Hogwarts. He uses his skills and knowledge to keep them safe, and if anyone tries to come between them, he'll use his wit and magic to drive them away.