[KRX]

Faiz did a really good job explaining its own science. However, I need to explain some concepts. The Photon Blood is at different concentrations from Rider Gear to Rider Gear. Delta's is the most raw, Psyga and Orga's is the most pure, and the other Gears are in between. When in contact with Orphenoch cells, the Photon Blood creates a chemical reaction that generates the suit's material. The belt is designed to make the material form around the Rider the proper way (with a little help from some nanobots). However, Orphenoch cells are burned in this process. Usually, Orphenochs are able to generate cells fast enough so they don't die. However, humans with Orphenoch cells need more time to regenerate these cells before they die (hence why Masato bit the dust). The purer the Photon Blood, the more Orphenoch cells you need. If you don't have enough Orphenoch cells, the Gear will not work for you. In the case of Delta, however, any kind of cells can be used, so long as they're human-derived (since Orphenochs are evolved humans). Humans are able to generate enough cells at a fast enough rate so that they usually cannot die from using the Gear. (Note how I say "usually.")

P.S. The only reason I don't specify the material created is because it varies between Gears.