Genshin Impact: Klee's Little Sister Is Ridiculously Strong

【Pure story-driven (the plot is somewhat complicated, so a few spoilers are necessary) + Not mindless + Not invincible (he isn't especially strong from the start, and sometimes loses, but always with honor) + Sound values】 Alternate title: My Soul Transmigrated into Klee's Little Sister, and I Became Teyvat's Savior After an accident, Ke Ran Bing transmigrates into Klee's little sister, Ke Bing, and becomes a new member of the Knights of Favonius: the Iceflower Knight. Judging by Klee's impression of her sister, Ke Bing seems like a sweet, fragile little girl. But behind that facade, she was once the Fatui's Twelfth Harbinger, a ruthless figure who even helped Mondstadt steal back the Anemo Archon's Gnosis while undercover. Later, she meets Alice and discovers that Alice knows magic that lets her travel back and forth to the modern world, where she can obtain modern items. Alice finds a spellbook containing power far beyond that of the Heavenly Principles. Said to have been written by a god named Truth, it soon grants Ke Bing strength rivaling that of the Cryo Archon. Thanks to this spellbook, the people of Mondstadt become completely immune to the curse of Forbidden Knowledge in the restricted section. They dare to explore the secrets beyond the world, driving Mondstadt's technological development forward. The weakest nation soon rises to become a power capable of standing toe-to-toe with the Fatui. But to fully unleash the book's power, overthrow the Heavenly Principles, and raze the Abyss, there is only one option: find the Traveler, who mysteriously vanished for unknown reasons... (A quick heads-up: the plot logic in the middle and later parts is a bit like World War II, and may include a trope similar to “Mondstadt's lightning-strike invasion of Fontaine.”)