The initial idea or setting of this author works are great but as the plots progress, it's 90% smut and 10% plot each progress.
This manhwa may end probably in 150 chapters if the pace are this slow.
If zombie broke in 20, MC either separate from his group and move with ML which can make another 20 chapter of fcking MC or MC and ML will be separated there which can make 5 or 10 chapters and then ML appeared, fck MC for 20 chapters and then he disappeared again or MC ran away and make another 3 or 5 chapter before ML appeared again. Plot twist coming in causing 50 chapters where ML probably the origin of corrosive and he might be the antidote. Thanks to ML fking MC, MC gain immunity or smthng. With pyscho ML are, he doesn't want to help mankind so researcher may aim at MC instead, make him as experiment subject. ML rescued while fcking him.