From the Start, I Transmigrate into Naruto, and the System Grants Me Immortality

[Immortality + invincibility + leveling up + everyday life in the ninja world + no female lead] (Gentlemen, don’t skip chapters. Read the synopsis before deciding whether to read. This is a slice-of-life story.) (Some plot points have been significantly changed. Please bear with me!) Changqing transmigrates to the world of Naruto and awakens an immortality System, which gives him a chance to allocate stat points once a month. With an infinite lifespan, all Changqing has to do is stay alive to become invincible. The System also gives Changqing a mission: help Naruto and Sasuke defeat the Otsutsuki clan. Unfortunately, the System sends Changqing back a little too far. He transmigrates to the Warring States period, the era of Madara and Hashirama’s parents… During the Warring States period, Changqing befriends Uchiha Madara and Senju Hashirama, and unexpectedly becomes their teacher. Changqing is connected to the founding of Konoha and the end of the Warring States period. He is the teacher of the God of Shinobi and the Demon of the Shinobi World, the living embodiment of legend, and the very definition of immortality… Senju Butsuma: “Big brother Changqing, you don’t seem to be getting any older.” Uchiha Madara: “Teacher, perhaps your way of thinking is right, but I can’t turn back now.” Hatake Kakashi: “Senior, if it weren’t for you, I really might never have had the chance to see Obito again!” Uchiha Sasuke: “The burden of reviving my clan rests on my shoulders. Please teach me your techniques, Teacher!” …