For the BTD6 counterpart, see Ninja Discipline (BTD6).
$300 (Medium) $325 (Hard) $360 (Impoppable)
Ninja Discipline is the first upgrade on Path 1 for the Ninja Monkey. It costs $255 on Easy, $300 on Medium, $325 on Hard, and $360 on Impoppable.
In BTD5, this upgrade increases attack range and attack speed of a Ninja Monkey from one attack every 18 frames to one attack every 15 frames, giving it 20% more attack speed. After upgrading, the ninja turns white with a black bandana.
Ninja Discipline is an extremely cost-efficient early game tower.
Seeking Shurikens will allow it to use its popping power fully. They are usually used to lead into higher tier top path Ninjas. Ninja Discipline will also increase the rate of Distraction applying, and will also increase the attack speed of Flash Bomb, so it is recommended to crosspath this path for those towers.
In BTD5, the upgrade picture is of a white scroll with illegible writing.