What does Turbo Mode do?
According to Nintendo Life, Turbo Mode is a sped-up challenge mode unlocked after beating stage nine in Normal Mode.
After beating stage nine you'll unlock Endless Mode (play through all stages consecutively - if you can!) and Turbo Mode, which is a sped-up version of the game. Beating all the stages in Turbo Mode will unlock an "endless" version of Turbo - nice to have when you're looking for that extra bit of challenge.
Review: Tomena Sanner - Nintendo Life