Soulcrystal
I'll be honest you really kinda overdid it on the training. He doesn't need every jutsu and affinity in existence, he just needs some to specialize in for now, and can branch out in the future. Also this novel is called Naruto: The Twin Flashes, but now one of them is massively overpowered, and the other has had no improvement at all.
Really comfy story author. I liked it. Although hiruzen giving him so much access even as a joke/test was too much. I don't think anyone would've included flying thunder god, but oh well. You should stop and ignore the waifu retards who wants MC to put his di*ck their favourite waifu(like tsunade lmao). If they want such ships they should go and read hentai stories. There are plenty of them around. I think it's far too soon to think about romance, but if you want to write about it and there's no one in your mind karin or samui(both underused) can be a good choice. Harem wouldn't suit the story. I also saw many commenters being stupid and confusing fanfic tropes with naruto canon like namikaze clan(lol), and people who want MC to be gray stu character and OP from the moment of his birth. You should ignore them as well. They're being retards. Overall it's a good story. Gamer powers are OP so him getting so strong is understandable, but at the same time so much strength would ruin the plot. I don't think MC changing plot and not affecting the bigger arcs and plot points can be justified. Hope you give faster updates.