Popular 3DS homebrew apps like PKSM (a portable Pokémon Bank alternative) require the latest game definitions to read your party data correctly without corrupting your inventory. How to Install the Update 1.5 CIA Safely
Applying the 30.25 MiB Update 1.5 CIA package via customized 3DS hardware is vastly superior to running the unpatched base game.
"Pokemon X Update 15 CIA Better" appears to refer to a fan-made or community-distributed update/patch for the Nintendo 3DS title Pokémon X, packaged as a CIA file (installable ROM format used on modified 3DS systems). This review assumes the update aims to improve gameplay, bug fixes, or add quality-of-life features over the original release.