Based on the facts that the mechanism of early matchlock guns is similar to that of the choju (guns for bird hunting) of Southeast Asia with a pressurized serpentine arm and the use of matchlock guns in Southeast Asia preceded to use in Japan, some researchers (such as Takehisa UDAGAWA) argue that matchlock guns were introduced into Japan not via Europe, as typified by the introduction of firearms to Tanegashima Island, but through illicit trades with Southeast Asia by wako.
鉄砲の伝来は、初期の火縄銃の形式が東南アジアの加圧式火鋏を持った鳥銃に似ている事や東南アジアにおいても先行して火縄銃が使われていた事などから、種子島への鉄砲伝来に代表されるようなヨーロッパ経由でなく倭寇などの密貿易によって東南アジア方面から持ち込まれたとする説がある（宇田川武久説）。