I Build NIKKEs in the Apocalypse

I just transmigrated, and the apocalypse has only seven days left. A nuclear strike right from the start? What's there to panic about? The System awakens and gives me an SR NIKKE, Rapi, right from the start! While everyone else is fighting tooth and nail over a bottle of water, I'm already getting ready to build the strongest fortress of the apocalypse with my gorgeous, badass NIKKE wives! Outside the bunker are nuclear winter and man-eating monsters. Inside is my own apocalypse paradise, full of armed beauties who only follow my orders! “Commander, what's the next mission?” “Don't rush. Come take a bath with me first.”