Chapters 12-13 (Normal)

Chapters 12-13 (Normal) is a secret achievement in the first Bayonetta game that is unlocked by completing Chapters 12 and 13 on Normal.

Description
"Complete Chapters 12 and 13 on Normal difficulty"

Guide
Just beat Chapters 12 and 13 on Normal.

Here is the wiki Walkthrough:

Chapter 12

Chapter 13