The "Kuru-toga" engine is a newly developed mechanism focusing on the tip of the mechanical pencil. The mechanism's inside is divided into three gears, and the middle gear connected to the pencil lead moves up and down using the writing pressure when writing letters. The middle gear and pencil lead rotate gradually each time you write a stroke by engaging the upper and lower gears diagonally.
The Kuru Toga Advance series has an updated "W Speed" mechanism, which rotates the lead twice as fast as standard Kuru Toga pencils so that the lead gets sharpened twice as quickly. The Advance series also features a metal sliding lead sleeve that guards the lead when you write. The sleeve will slide as the lead gets shorter or longer. The sleeve can also be fully retracted when the pencil is unused.