HELP PLEASE!!! orz

I remember this one manhwa where the MC entered a book world and met a woman and a man. The world was full of snow and zombies, and they would move only at night. The woman and the man kept fighting like children, but they were actually peerless masters who only looked stupid because they were using all their internal energy on staying alive and preventing the zombie virus from infecting them. The MC then became the woman’s disciple, but he had to collect memories(?) from dead people all over the snowy world so he could understand and feel what it was like to starve, thirst, choke to death etc. before he finally learns the martial art. Reading this was so bittersweet to me and I cried for real, but I totally forgot the title since it was a year or so ago when I last read it. Please help me! Thank you so much! orz