Perhaps Natsu goes on a journey to find other dragon slayers who might know more about his dual nature. Along the way, he meets new characters, some friendly and some not so much. This journey could also lead to him learning about a hidden prophecy related to dual dragon slayers and their role in saving the magical world from an impending doom.
One idea could be Natsu exploring a new magic ability related to his dual dragon slayer powers. For example, he discovers a way to combine the fire of his Igneel - taught magic with the other dragon's element in a more powerful and unique way.
A plot could revolve around Natsu facing a villain who also has some connection to dual dragon slaying. This villain could be a former apprentice of the dragons who turned evil, and Natsu has to use his skills and the bond with his friends to defeat him. Natsu might have to learn more about the history of dual dragon slaying to find the villain's weakness.
Chapter 88 is the strongest chapter-level answer because it starts from She wanted to refuse, but didn't have the courage to do so. and follows through on Let's go," Jiang Li said in a soft voice..
A practical answer is Chapter 74, because it turns the idea into a concrete scene. The chapter opens with Having seen Jiang Li's ID before, he knew that this person named Shiguang..., adds pressure through It's not just a banner we are talking about;
If you want the clearest chapter reference, go to Chapter 149. Early on, Seeing that Zhang Cheng's glass was nearly empty, Du Qinglian immediately...; later, the chapter leans on Director Zhang, this Zuichun Mountain is a specialty of Bi Garden, brewed....
The best chapter pointer here is Chapter 88, "I Call This a Test of Your Will!". It opens with She wanted to refuse, but didn't have the courage to do so. and closes on Let's go," Jiang Li said in a soft voice..
Look to Chapter 99 for the clearest answer. It begins with Seeing the man approach, one of the individuals with a long scar across..., keeps building through How is it, have those people outside left?" "They're gone." The man spat..., and lands on Just as she was considering whether to practice a.
The best chapter pointer here is Chapter 92, "Why would a 19-year-old girl read this kind of book?!". It opens with Jiang Li, lightened from any task, had plucked a few leaves from the... and closes on Finally, someone entrenched in the circle couldn't hold back and sent a....
The best chapter pointer here is Chapter 84, "Is it Just About Having Hands?". It opens with When the villagers tasted his curry beef one by one, their faces revealed... and closes on Why am I tasting sand in my mouth?" Wen Jiaojiao's bravado gradually....
Look to Chapter 119 for the clearest answer. It begins with What is Princess Wen talking about?, keeps building through I can't understand a word?] [Is this some new meme?] [!!!, and lands on For some reason, he always felt there was a mysteriously calming power....
Chapter 124 is the strongest chapter-level answer because it starts from Since there were too many points cards inside Jiang Li's barrel, Director... and follows through on No need to repeat that number three times.] [Hang on, didn't Jiang Yan....
Look to Chapter 95 for the clearest answer. It begins with Hearing others praise her daughter, Aunt Lin was smiling so wide she..., keeps building through Lingling really is a good child., and lands on Your boyfriend must have studied in another province, if I'm not mistaken,....