Since it's a fan - made work, the main characters could be entirely new characters created by the author. However, if it adheres to the general idea of combining Naruto and Twilight, we might expect to see Naruto as a central figure. He could be on a quest related to the 'twilight key'. And maybe he teams up with a Twilight character like Alice, who has the ability to see the future. They could be the main characters trying to figure out the mystery of the key and how it affects both their worlds.
I don't know for sure as it's a fanfic. It could have Naruto and Sasuke from Naruto, and perhaps Edward or Bella from Twilight if it's following a more traditional combination of characters from both series.
The main characters could also be secondary characters from both universes that are given a more prominent role in this fanfic. For example, Shikamaru from Naruto could be a key player. He's known for his intelligence, and in this fanfic, he might be the one to figure out the true nature of the 'twilight key'. From Twilight, Jacob could be involved. He's strong and has his own set of powers. The two of them might be at odds or working together in relation to the key and the events it sets in motion.
Chapter 259, "Is there, something dirty?!", is the clearest early answer because it turns Chixia Village's situation into a concrete plot event. It opens with While the villagers of Chixia Village were all immersed in the... and closes on It wasn't that he was scared..
Chapter 339, "The Changes in Li Hu and Yang Zhong, the Hou Family's Opportunity, and Advice (Part 2)", is the clearest early answer because it turns Yang Zhong's situation into a concrete plot event. It opens with According to the balance of their Contribution Value, it is actually... and closes on Considering your high Martial Arts Talent, it should be Battle Body....
Chapter 17, "Madam, the eldest young master has disappeared again", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event. The chapter gives readers a real answer by opening on Jiang Li glanced at Jiang Shixu, who was tense and anxious behind...
Chapter 338, "Rapid Progress, Martial Arts Skills, Dual Advance Eastward, Dormancy Period", is the clearest early answer because the buildup finally cashes out in a real clash. The chapter turns that into something concrete by moving from Lu Yang poured out everything he knew in one breath. to If we continue exploring east along the Xing River North Bank,....
Chapter 3, "Madam, the eldest young master has been missing for over half a month", is the clearest early answer because it turns Qiao Shuang's situation into a concrete plot event. Early on, Qiao was still annoyed at the attitude of this unknown girl when she....
Chapter 350, "Methods to Improve the Peak of Cold Resistance, Moao's 10th Town, Beishuo Yang Fa, Nightmare, Lu Yun of East Ridge", is the clearest early answer because it turns Nightmare Monster's situation into a concrete plot event. It opens with Hmph, the Nine Towns have had an agreement long ago: if a Xianyang... and closes on Evidently, the other party didn't believe his self-introduction just....
Chapter 341, "Moao's Nine Garrisons, the Inspection System and Zhenyu, Li Hu and Hong Yuru (Part 2)", is the clearest early answer because it turns Cold Resistance Level's situation into a concrete plot event. The setup is Lord Wang is not wrong, but not entirely right either., but the pressure keeps building through The Nine Towns all adopted the inspection system first created by....
Chapter 272, "Jiang Fugui", is the clearest early answer because it turns Jiang Fugui's situation into a concrete plot event. The chapter turns that into something concrete by moving from Lin Manru held the phone for a few seconds, expecting her daughter...
Chapter 219, "Five Thousand Jin??!!", is the clearest early answer because it turns Director Sun's situation into a concrete plot event. The chapter turns that into something concrete by moving from Qi Tianyu was somewhat freaking out.
Chapter 137, "Lai Fu's Death Has Another Cause", is the clearest early answer because the violence around Yintang becomes final instead of hypothetical. The chapter turns that into something concrete by moving from Jiang Li personally went to Lai Fu's tomb and performed a small...