Here is the full list of all 25 Yoiyami Dancers: Twilight Danmaku Dancers achievements.
Finish the tutorial.
Finish Scenario #1 on Cheerleader (Normal) level or harder.
Finish Scenario #1 on Breakdancer (Hard) level or harder.
Finish Scenario #1 on Backdancer (Lunatic) level.
Achieve a Full Combo on any stage before the boss (only the first beat can be skipped).
Reach 30 Attack while playing Scenario #1 (Graze boost excluded).
Finish Scenario #1 with less than 10 Attack (Graze boost excluded).
Accumulate the Graze count of 100 or more (outside of the tutorial).
Land 8 consecutive attacks without being hit in Scenario #1.
Use Charge attacks to deal more than 80% during a boss phase.
Finish Scenario #2 on Cheerleader (Normal) level or harder.
Finish Scenario #2 on Breakdancer (Hard) level or harder.
Finish Scenario #2 on Backdancer (Lunatic) level.
Clear two stages without looping through Flower Powers.
Let a bullet pass through you while powering-up.
Use any Flower Power after looping more than 8 times (when "x9" appears) when not using the White Flower.
Finish Scenario #2 with less than 10 Attack (Graze boost excluded).
Use "Wide Attack" three or more times to defeat an enemy not in your row.
Use "Spear Attack" to damage four enemies at once (overlapping enemies count as one).
Use "Multi Attack" to defeat an enemy with 3 or more shields in a single hit.
Try any Boss Attack in Practice Mode.
Get one Gold Medal (any difficulty).
Earn 20 Medals from Boss Attacks. (Different difficulties of the same attack do not count as separate medals)
Earn 40 Medals from Boss Attacks. (Different difficulties of the same attack do not count as separate medals)
Beat any boss attack 5 times in a row without taking damage in Practice Mode(not available during Rehearsal mode).