1. Uchiha Itachi: Itachi, a genius ninja in the Naruto series, faces high expectations from the Uchiha clan and Konoha officials. However, his young age brings about an illness that weakens his physical condition. This ultimately leads to his death due to the strain of ninjutsu usage.

2. Orochimaru: One of the legendary ninjas, Orochimaru's physical condition is inferior to Jiraiya's. His constant experiments on his body in pursuit of eternal life result in poor physical condition, as he frequently replaces his own body.

3. Kimimaro: Initially chosen as a potential new body by Orochimaru, Kimimaro is gravely ill, preventing the fulfillment of Orochimaru's plan. Constant medication is used to prolong his life, but his body is already on the verge of death.

4. Tsuki no Haya: A high-ranking ninja and examiner in the Chuunin Exams, Tsuki no Haya suffers from illness but not to the same extent as Itachi. He compensates for limited chakra reserves by focusing on training in Konoha-style Swordsmanship. 5. Onoki: As the Third Tsuchikage of Iwagakure, Onoki is the oldest ninja alive. Though he once challenged Madara Uchiha, time has affected his abilities, and he has aged. Now an elder in the ninja world.