Printing systems with an information-display function are attracting increasing interest as greater volumes of information become available in digital format. We recently developed a practical rewritable printing system for displaying documents in which the coloring-decoloring reaction cycles are thermally controlled using leuco dyes. This system is composed of leuco dye molecules and acidic developer molecules with long-chain alkyl groups and associative groups; it exhibits colored/decolored states that can be reversed by varying the heat conditions. Since the reversibility property mainly depends on the molecular structure of the developer, we prepared simple developers with different alkyl lengths to investigate the structural effects. We found that controlling the physical properties of the long-chain alkyl group of the developer is the key to achieving both thermal stability of the colored state and rapid erasability.