if you haven't started doing any of the martial arts, I suggest you should do kendo first. Through my experience, the kendo movements are more active and hard to coordinate. Iaido, on the other hand, is calmer. If you learn kendo properly, it is easier to do iaido.

Iaido is not unified, so there's no single ranking system. There are, however, some more common ones like the kyu-dan system used by the International Kendo Federation (FIK) which was inspired by the system used in Judo, but uses no visible indication of rank like coloured belts.

Iaido consists of four main components: the smooth, controlled movements of drawing the sword from its scabbard (or saya), striking or cutting an opponent, shaking blood from the blade, and replacing the sword in the scabbard.

The Japanese martial art - Iaido Practitioners of the art - Iaidoka - use real katana (or blunt training swords - Iaito - which are still quite dangerous), so it is primarily a solitary art.