If you saw this phrase attached to a Steins;Gate product, it almost certainly refers to a exclusive to a retailer called Codex (or a special "Codex Box").
Exclusive Steins;Gate content, often referred to in enthusiast circles, is primarily found in the Elite Limited Edition, featuring a storyboard book and platform-specific bonus games. Community-driven "Committee of Zero" patches restore cut content, while exclusive, retailer-specific print editions exist for the Steins;Gate 0 manga. For a detailed look at the limited edition, watch this video from Spike Chunsoft . steins gatecodex exclusive
praise the Codex for finally explaining recurring plot holes—specifically why Moeka’s D-Mail behaved differently than the others (the Codex reveals her phone used a different quantum encryption protocol). If you saw this phrase attached to a