Well, from what we can tell, Hinata is the central character as the title starts with 'legend of hinata'. Naruto is also likely to be a main character as the title mentions 'a naruto'. In addition, there might be antagonists or supporting characters from the Naruto series. For instance, characters like Sasuke could potentially be involved, either as an ally or an obstacle in Hinata's journey to the past, depending on how the author writes the fanfiction.
Based on the title, Hinata is surely one of the main characters. And since it's related to Naruto, Naruto himself is likely to be an important character as well. There could also be other characters from the Naruto universe, like characters from Hinata's clan such as her father or sister, who might play significant roles in the story as it involves Hinata's journey to the past.
Definitely Hinata is a main character. Given that it's a Naruto - related fanfiction and it has 'to the past' in the title, it's possible that older versions of known characters could be main characters too. For example, the younger versions of Naruto's teachers like Iruka Sensei might be important characters. Also, characters from Hinata's past, like her mother (if she's introduced in the fanfiction), could be main characters as well, as they could be related to the events that Hinata is going to experience in the past.
Chapter 108, "Without accumulating virtue through words, calamities of bloodshed will only increase, not decrease.", is the clearest early answer because it turns Su Yinwan's situation into a concrete plot event. It opens with In a glamorous Michelin three-star restaurant, Su Yinwan and Shang...
Chapter 262, "Flash Change Quartet Speaks Out for Jiang Li", is the clearest early answer because it turns Weibo's situation into a concrete plot event. Early on, Wen Jiaojiao couldn't stand it anymore and immediately logged onto.... By the end, Your manager restricts that as well?.
Chapter 58, "Jiang Yan Stranded Abroad", is the clearest early answer because it turns Jiang Yan Stranded's situation into a concrete plot event. The chapter gives readers a real answer by opening on Facing Jiang Yan's triple barrage of questions, Jiang Li's only...
Chapter 120, "Jiang Li Can Actually Do Acupuncture?!", is the clearest early answer because it turns Is Jiang Li's situation into a concrete plot event. The chapter gives readers a real answer by opening on Facing the sudden and somewhat strange request from Jiang Li,...
Chapter 164, "Congratulations to Jiang Yan for scoring one point!", is the clearest early answer because it turns Congratulations's situation into a concrete plot event. The chapter gives readers a real answer by opening on Damn, the production team is so shady, they're still doing a live...
Chapter 85, "They must have been bought off by Jiang Li!", is the clearest early answer because it turns Is Jiang Li's situation into a concrete plot event.
Chapter 483, "Why Does a Pig Eat M9?!", is the clearest early answer because it turns Yu Li's situation into a concrete plot event. The chapter gives readers a real answer by opening on Wilderness Survival Day 11, temperature 31 degrees, wind speed...
Chapter 216, "I'm the Director, I Call the Shots!", is the clearest early answer because it turns Wen Jiaojiao's situation into a concrete plot event.
Chapter 34, "Official Recording!", is the clearest early answer because it turns Shining Transformation Trip's situation into a concrete plot event. The chapter turns that into something concrete by moving from Seeing that the public sentiment wasn't quite right, Su Yinwan felt...
Chapter 347, "Mirror Valley Council, Power Surge, Dajue Temple, Eight Battalion Tournament (Part 3)", is the clearest early answer because it turns Cold Beasts's situation into a concrete plot event. The chapter gives readers a real answer by opening on Every time a new division of the army is established at the camp, it... and ending on What Xia Hong mentioned now coincided exactly with his thoughts as he....