"Alchemy" is a pseudo-science that attempts to create "gold" from various different combinations. Nagisa Misumi formerly Cure Black, is entrusted with the Gotchadriver and the mission to recollect the Chemys that have been released into the world. Some are well suited for human companionship and if resonated with a good heart, Nagisa can fuse with them and transform into Kamen Rider Gotchard!
3 parts