Gear 3 Episode File

: Luffy bites his thumb to create a small opening and blows air into his skeletal system, a technique he calls Hone Fuusen (Bone Balloon).

It sounds like you're referring to a review that discusses — likely from One Piece (where Luffy's Gear Third debuts in the Enies Lobby arc, episodes 304–305 or so), or possibly from another series (e.g., Boruto or a mecha anime). gear 3 episode