Plant myosins have higher velocities than animal myosins. Among them, myosins in freshwater algae of the genus Chara have extremely high velocities. We have biochemically studied myosins that perform high-speed movements in the alga Chara. Our studies have elucidated the structural and enzymatic basis for the fast movement of Chara myosins. This review outlines the history leading to the discovery of the fastest myosin, algae Chara myosin XI, and the structure-function correlation of the fastest myosin. This review article is an extended version of the Japanese article, "Structure-function Relationship of the Fastest Myosin" by Ito et al., published in SEIBUTSU BUTSURI Vol. 63, p. 91-96 (2023).