Corporate drone Lin En dies of overwork from working overtime, crossing over into another world to become the weakest slime, binding the Devour Evolution System, and being contracted by the waste-vein girl Ai Linna. The two rely on each other, constantly evolving all the way by devouring monsters and ores, and get to know the Silver Wing Squad to adventure side by side. Along the way, they expose the Ai Lin family bloodline curse and the Demon King's past, fight against the noble Ka Luosi and church forces, Lin En breaks through to Demon King seed, fuses with divinity, and finally says goodbye to his own divinity which has turned into the world guardian, stays together with Ai Lin, and walks out on their own free path.