"One Piece: Sign-In at the Start to Get Ryūjin Jakka"

Roya transmigrated into the world of One Piece, and right from the start, he found himself trapped inside Doflamingo’s Birdcage. Fortunately, he awakened the Sign-In System and obtained the strongest fire-type Zanpakutō—Ryūjin Jakka—from the very beginning! "All things in the universe turn to ash—Ryūjin Jakka." With flames reaching the heavens, his name spread across the seas! Five Elders (Gorosei): “Damn it! Who is this guy constantly getting in our way?!” Sengoku: “That man must be hiding some unspeakable scheme!” Akainu: “His flames… actually managed to hurt me?!” Shanks: “This man is definitely someone worth allying with!” … As he continues signing in on different islands, all kinds of god-tier rewards begin to appear. From that moment on, across the Grand Line—I am the strongest! Main Characters: Roya, Kalifa, Zephyr, White Dove