Here is the full list of all 22 TENSEI achievements.
Attain Dragon Form for the first time
Reach Spring scenery
Reach Summer scenery
Reach Autumn scenery
Reach Winter scenery
Reach an answer
Attain Dragon Form 15 times
Attain Dragon Form 150 times
Attain Dragon Form 300 times
Die from touching something
Die from falling
Purify worldly desires 100 times
Purify worldly desires 500 times
Purify worldly desires 1000 times
Achieve a Zen state
Get help from "Red Charm" powers
Get help from "White Charm" powers
Gain free mobility
Reach a score of 25,000
Reach a score of 100,000
Reach a score of 500,000
Strive for greater heights time after time.