The art of bloonjitsu allows Ninjas to throw 5 shurikens at once!
Bloonjitsu is the final upgrade on Path 1 for the Ninja Monkey in BTD5, allowing the Bloonjitsu Master to throw 5 shurikens at once.
In BTD6, this upgrade returns, but it now cannot have both Distraction and Seeking Shuriken at the same time. Again, Bloonjitsu allows the Ninja Monkey to throw 5 shurikens per shot instead of 2. It costs the same price as in the original game.
Adding many 4/2 Bloonjitsus are extremely reliable against distracting Ceramics and lower bloons, especially in Freeplay Mode.
There is no reason not to get the Path 2 upgrades because these two upgrades are both really useful for providing both accuracy (via Seeking Shuriken) and a high chance to distract bloons (via Distraction)
Since DPS and shuriken accuracy via Seeking Shuriken are generally more important than a spray of shurikens with a chance of distracting bloons via Distraction, it is best to go along Path 3 instead of Path 2.
Bloonjitsu Ninjas are among the best candidates for Berserker Brew and Stronger Stimulant, even after the Version 6.0 Alchemist nerf. This is because they don't shoot so fast as to expire potions so early but at the same time shoots many projectiles at once with good overall pierce and damage. As a result, it is recommended that Bloonjitsus are not upgraded to the Grandmaster Ninja, and are not in range of any Shinobi Tactics ninjas, as these will cause the ninja to use up the buff quicker.
This upgrade used to be indirectly cheaper to get in BTD Battles Mobile thanks to Sharp Shurikens and Double Shot getting their prices decreased. However, since update 4.9 the overall cost to get a 4/x Ninja Monkey is now the same as in BTD5.
The Bloonjitsu can shoot every 0.42 seconds without any bonuses from the Monkey Lab.
The cheapest possible 4/2 Bloonjitsu in BTDB Mobile normal battles is $4500 in between Version 4.1-4.5, obtained from discounting the original price of $5000 ($500 + $300 + $250 + $250 + $400 + $550 + $2750) by a Village.