The required rate for the last mission “B O n u S” was 99.90% on day 1, which made it extremely hard.
However, the required rate dropped to 99.50% since day 2, so it is now not that hard. Still a little hard, but won’t be really a problem, once you got used to the rhythm.
I tried several times, and finally got 99.4x% on one try and 99.5x% on the next try. If you find it hard to catch the rhythm, try reading bar lines.