It's not that he doesn't like to laugh, it's just that he's too lazy to stretch his laughing muscles. It's not that he can't run fast, it's just that no one is chasing him. It's not that he's not afraid of death, he's just too lazy to even care about death.
See how a lazy man survives in this extremely dangerous world
Naruto version
Uncle Snake: "Mu Dun's body! What a dream physique! Do you want to come to our place?"
Xiaofeng: "Do you include food, accommodation, and wages?"
Uncle Snake: "..."
One Piece Edition
Luffy: "Xiao Feng, come to my boat! I don't mind your laziness!"
Xiaofeng: "But I mind your hard work!"
Luffy: "..."
Tutoring Edition
Li Baoen: "It's pretty awesome. Come to Vongola!"
Xiaofeng: "If I can get paid without working, I will go."
Li Baoen: "..."
Death Edition
Byakuya: "Why haven't you learned Shunpo yet?"
Xiaofeng: "Let me sleep for another 48 hours and I will study."
Byakuya: "If you learn how to steal desserts from the dessert shop in the west, you won't be caught!"
Xiaofeng: "Teacher Byakuya! I will definitely become a qualified god of death! "
Byakuya: "..."