Here is the full list of all 31 Dokuro achievements.
Defeat 100 monsters in Skeleton Form.
Use blue chalk successfully.
Complete stages 5 to 8.
Collect 75 coins.
Pick up the Princess 200 times.
Light 4 torches with a single red chalk.
Collect 50 coins.
Complete stages 1 to 4.
Use red chalk successfully.
Collect 25 coins.
Collect 10 coins.
Use white chalk successfully.
Collect your first coin.
Unlock all achievements.
Collect all coins.
Complete all areas in a total of 250 minutes or less.
Defeat 1000 monsters in Hero Form.
Complete stage 14 without taking any damage.
Complete all areas in a total of 350 minutes or less.
Fall from a great height.
Collect 135 coins.
Collect 120 coins.
Collect 100 coins.
Complete stage 11-5 without being discovered once.
Complete all stages.
Defeat the Dark Lord without taking any damage.
Complete stages 9 to 11.
Complete stages 12 to 15.
Die 100 times.
Successfully deflect boomerangs 100 times.
Let the princess get knocked out 100 times.