Original God: Becoming the elder brother of the Thor twins

The early plot of this book is original, as the author cannot verify it. Don't criticize if you don't agree. (The author herself feels the early plot is poorly written; feel free to skip to Chapter 20.) Upon traveling to Teyvat, Raidenshi is far from happy. Being transformed into a baby is one thing, but the time period seems off as well. Why are there so many demon gods? Where are the Thunder Twins? Raidenshi, nearly attacked by a wild boar, panics. Luckily, he's rescued by an older sister. With no special abilities, is he destined for a mediocre life? Just when Raidenshi is ready for his future, a surprise arrives—this is the author's first time writing a book, and he's not very experienced...