Request for help identifying a movie...

Hello! I'm new here and not sure if this is the best place to post this, but here goes...

I am trying to find a very particular movie that I saw once on television many, many years ago.

I would place the time frame somewhere between 1985 and 1991.

I don't have much to go own - only memories of specific scenes in the movie.

It's a "Ninja" movie - popular to the mid to late 1980's.

It's about an orphaned caucasian baby boy who is dropped off on the front porch of an old (middle aged?) Japanese Ninja master's front porch.

The Ninja Master takes the orphan baby in and first tests to see if the baby is "worthy". The Ninja Master throws the baby into a pool of water to see if it can swim or drown. The baby swims, therefore is found worthy.

As the child grows, the Ninja training begins.

One scene depicts a cat silently walking on the front porch. The young boy try's to imitate the cat by walking silently but causes the board to creak. The Ninja master shows the boy how it's done.

Another scene later in the boy's life shows him and the Master driving to town where a fight breaks out between some white guys. With very minimal effort the Ninja Master takes them all down. The boy was astonished that the frail old man could do such a thing. The Master tells the boy something profound; something to the effect (paraphrase) of, "A butterfly could kill a man if it only knew but where to place its wings."

Later we see the boy grown to adulthood living in a "modern" home. This is where my memory gets fuzzy on the details.

I believe he is married, or has a girlfriend, or some other "companion"/"partner" or sorts.

He must go on some mission (perhaps for hire as an assassin?) to deal with some corporate executive type who needs a proper shakedown, Ninja style.

The caucasian Ninja guy traps the executive and his henchmen in a high rise building and he does what Ninjas do... He chases, and hunts, and tracks, and scares the executive until they reach the climactic end scene.

This end scene involves the Ninja taking a gun from someone and handing it to the executive - possibly as a show of "leveling the playing field". When the executive thinks he has the upper hand and tries to shoot the Ninja point blank, nothing happens and the Ninja opens his palm and reveals that somehow, he secretly unloaded the gun.

Also during this whole thing, I believe someone else, possibly a detective or FBI is investigating the Ninja guy to see if he's an assassin? But when events unfold, the Ninja guy is found to be home the entire time. In reality, it was his assistant/partner who masqueraded as the Ninja guy at home to create an alibi.

Anyway - that's all I remember about the movie, some scenes, and the approximate window of time when I saw it.

I don't suppose anyone here might know which movie this might be.

Kind regards, and happy New Year!