To unlock ten bonus chapters, complete all fifty single-player episodes.

To unlock an N+ Gamerpic featuring a black ninja with a red headband, complete the ten bonus chapters.

ACHIEVEMENT - HOW TO UNLOCK
Complete 15 Episodes (10 points) - Complete 15 single-player episodes.
Complete 30 Episodes (15 points) - Complete 30 single-player episodes.
Complete 40 Episodes (20 points) - Complete 40 single-player episodes.
Complete all 50 Episodes (25 points) - Complete all 50 single-player episodes.
Complete 5 Co-op Episodes (15 points) - Complete 5 co-op episodes.
Complete 10 Co-op Episodes (15 points) - Complete 10 co-op episodes.
Speed Demon (20 points) - Win 10 races in ranked online matches.
Survivalist (20 points) - Win 10 survival games in ranked online matches.
Disciple (5 points) - Complete one tutorial episode.
Perfectionist (20 points) - Complete an episode without dying in single-player mode.
Treasure Hunter (20 points) - Complete an episode and obtain every gold piece in single-player mode.
Practice Makes Perfect (15 points) - Die 1,000 times in single-player mode.