Luffy and his crew had gotten jumped by many marines and other pirates and ended up separated and on an unknown island which wasn't good. Luffy had no idea where his crew was and he was injured pretty badly the marines had some new devil fruit users he didnt expect to see so it caught him off guard and got him pretty fucked up

Now he was on the beach of the island washing his mouth out of sand as he dusts his clothes off and look at the island he had some deep cuts but he'll be fine as he went towards the village or town to see if he could find any one of his crew mates but he found something he didn't expect using his observation haki he could see someone or something in the forest and got excited for a new adventure and went into the woods

[This is post timeskip so hes 19 at this time]