Little Goku's Multiversal Adventure starts from Marvel

After defeating Mercenary Tao and the Red Ribbon Army at the World Martial Arts Tournament, Little Goku embarks on a three-year journey of training. Accidentally gaining the ability to enter different worlds, he embarks on a journey of training across the universe. Son Goku, the savior of the Dragon Ball universe, becomes the savior of all realms. Worlds: Marvel, Harry Potter, Demon Slayer: Kimetsu no Yaiba, Attack on Titan, Inuyasha, Akame ga Kill (2011), Jujutsu Kaisen, Fairy Tail, Naruto, One Piece, Bleach, Hunter x Hunter, The Elder Scrolls, Lord of Mysteries, Saint Seiya, and the DC Universe. — Description from novelcodex.org