Genshin Impact: the Diary of Teyvat by Enichi Kuni

Ji Guoyuan felt that he had picked up the wrong time-travel script. He closed his eyes and opened them again, and he was reincarnated directly into Inazuma, a samurai family that couldn't get enough of it. Okay, reincarnation is reincarnation, at least the name has not changed - Jiguo Enichi. The fringe benefits are all the belongings of the legendary swordsman in Demon Slayer: Breath of the Sun, Transparent World, and Patterns. The problem is, this benefit is given to the wrong person! In his previous life, he was just an ordinary social creature who played games and watched TV shows. He had an overly cheerful personality and was occasionally a bit sinister. After living in Teyvat for twenty-five years, I thought I would spend my whole life just like this - practicing my sword, teasing others, and occasionally muttering to the legend of General Thunder and Lightning. The result? My brother, Iwakatsu Tsukuni, didn't know which muscle was wrong, so he plunged into the abyss for strength, and was transformed into something neither human nor ghost under the experiment of that crazy doctor among the fools. It's better now. After Yuan Yiyi, a holder of the Eye of Fire God, whose strength is about 50% comparable to that of Thor, his current job is to hunt down the Abyss Order and Doctors in the entire world of Tiwat. To put it simply, it means working overtime. The knife on the waist is called the Sun Lun. It can't kill ghosts. After all, there are no ghosts, only ghosts. But it is very useful for killing monsters. As for the future? Just take a step and see. Anyway, that's how he is. He laughs when he should laugh, and he won't show any mercy when he should kill someone. (It's not Tsukuni Emoto himself, it's his ability. His personality is more like Tanjiro's. He was born to watch for himself. It's normal to make mistakes. He'll stop when he loses interest in this subject.)