Perhaps there was a curse or a disease that he couldn't overcome. In some fanfictions, they like to introduce unique and deadly diseases that not even the best medical ninja can cure. It could also be due to a failed mission where he was caught in a trap that was impossible to escape from, leading to his death.
It could be because of a betrayal. Maybe someone he trusted turned on him and led him into a deadly situation. Or there could be a situation where he was protecting someone dear to him, like a friend or a younger ninja, and in doing so, he put himself in harm's way and ultimately lost his life.
Chapter 138, "Mirror Immortal Strange, Cold Resistance Level? [3-in-1]", is the clearest early answer because Deception Detection Jade finally turns buildup into a real advancement. A useful checkpoint is the way the scene starts with When we just merged, the temperaments of the brothers He Meng and He... and follows through with I'll let He Meng cause some trouble first, and persuasion should be....
Chapter 117, "Teng Jiao Saliva and Poison Source [Two-in-One]", is the clearest early answer because it turns Teng Jiaos's situation into a concrete plot event. It opens with Although Teng Jiao is dead, the poison mist still hasn't dispersed... and closes on Moreover, if it had discovered us as soon as we entered the Cloud....
Chapter 204, "Homecoming, Unease, Avian", is the clearest early answer because it turns Xiang Liang's situation into a concrete plot event. Early on, Using millions of pounds of iron ore to make a gate?. By the end, With more information deduced in his mind, Xiang Liang's expression....
Chapter 142, "%, The Boiling Brought by the Martial Arts Training Ground [8000 Major Chapter Subscription Request]", is the clearest early answer because a shaky connection becomes usable in the plot. It opens with And those coming for the first time began to cultivate by imitation,... and closes on It should only take one more day to finish them up." Xia Hong nodded,....
Chapter 157, "The Disappeared Cold Beast, Breakthrough Tide", is the clearest early answer because Wood List finally turns buildup into a real advancement. A useful checkpoint is the way the scene starts with After setting the tone, he paused for a moment and continued:... and follows through with After pondering for a moment, Luo Yuan's eyes suddenly brightened,....
Chapter 147, "Total Kill, Confrontation Cold Resistance Level [Killing Spree Chapter, Seeking Monthly Tickets]", is the clearest early answer because Cold Resistance Level finally turns buildup into a real advancement. A useful checkpoint is the way the scene starts with Don't kill them all, leave some alive!" Xia Hong ignored the look in... and follows through with There's no reason why everyone in Mirror Immortal Camp who has....
Chapter 194, "A Tragic Scene, Ice Skin Jade Bone, Xia Hong's True Strength", is the clearest early answer because it turns Ice Skin Jade's situation into a concrete plot event. The chapter gives readers a real answer by opening on The people who had just scattered and fled didn't get far before... and ending on On Xia Hong's side, he began his assault..
Chapter 153, "The Terrible Color of the Dense Forest, The Shadow of Mirror Immortal Gu", is the clearest early answer because it turns Xia Hong's situation into a concrete plot event. The chapter gives readers a real answer by opening on Possessing over ten thousand population, and hundreds in the... and ending on Xia Hong slightly turned his body, using his back to receive the....
Chapter 209, "Dragon Sparrow Coldblood, Luo Ming's Sense of Loss", is the clearest early answer because the buildup finally cashes out in a real clash. Early on, A kilometer to the west of the valley, a black city wall running.... By the end, I had already arranged with him at Jing Valley as per the leader's.... Inside the broader exploration storyline, the chapter closes with "You can also try softening the land with coal stone and transplant some medicinal plants to test;
Chapter 216, "Miracle Medicine, Outing, and the Longyou Incident", is the clearest early answer because the rescue effort creates visible on-page results. A useful checkpoint is the way the scene starts with Unlike the first time entering the main building, this time, with... and follows through with No, even with the three medicines, we probably can't withstand the....