It Is Painful!痛いんです; Itain desu; Itai ndesu; Itai n desu

What level of pain can you tolerate? Is it 1? Or is it 6? Lets go to the theme park of pain A collection of painful events that people have experienced sorted in the Pain Level Scale, from 1 to 6. Note: Sukima.me lists there being 23 chapters because they merged 3 and 4. There are 24 chapters.