Mario goes on an adventure to save his world from an evil magician. The sequel of Paper Mario 5: The Rise of Shadow. Many new mechanics are introduced, like the day-night mechanic. (No spoilers until we write the whole thing...)
As usual, Mario was at home, eating his usual share of homemade spaghetti when a satisfying "ding!" came from outside. Mario trots outside to see that the "ding" came from the mailbox. Looking at the letter inside, Mario gave a joyous cheer. The Princess invited him on a royal vacation to Isle Delfino, a place he remembered well and knew that it was the best vacation spot in the Mushroom Kingdom. Mario rushed to catch the next plane to Delfino Plaza.
When Mario got there, he yet received another letter saying that Peach missed the final flight to Delfino. Now sad, Mario decided he should make the best of the trip and have fun anyway. He walked to the new Gelatto Cafe, grabbed an ice cream, and sat at the beach. Somebody named Magicio (Pronounciation: Ma-ji-sheeo) saw Mario and invited him to a magic show. Mario, thinking "why not?", sat down in a seat and waited for the show to start. Suddenly, a person with armor tore down the magic show stage and told Mario that it was a trap. Magicio, knowing he was chaught, ran off. The knight-like figure introduced himself as Sir Calibur. After Mario thanked him, Sir Calibur began to explain Magicios plot (he also says that Magicio likes to pull evil tricks on people for fun...). Magicio's real plot is to find all the petals of the legendary Sun Flower. Once the petals are joined to the stem of the flower, you can gain enough power to even break the invincibility of the StarMan (Mario shudders). Mario wants to help and Sir Calibur answers with a practice deul to train Mario.
Tutorial "Boss": Sir Calibur
Basically he teaches you all the fight mechanics.
After the fight, Calibur says he'll meet Mario again soon, and runs off telling Mario the 1st petal location... Delfino Forest