the age difference is more like 30 years. Maybe you are right, It is none of my business, I did nothing then because I did not know what to do. I left the dojo altogether; it has been years now; it hurt I helped build that place; I put a piece of my life in that school. Both people joined years later than I. I saw them together casually, out of class, recently, and it made me angry again, but I see that the "love" will be brought in as a justificaition. I am not going to speculate on what else goes on in their lives, as I see this, I am not going to be comfortable with any situation in which such difference in power exists. The dojo cho did not see fit to constrain the man , he must have concluded it is love.
What a hypocrite!
YOU allowed to happen this situation and now you blame everyone around (instructor, dojo and entire art of aikido!!).
You are part of society, and you have the rights and Responsibilities. "I did not know what to do' - no kidding? How about asking first police officer on the street - is that too complicated?
It is entirely your fault, you was not up to this situation, don't try to justify your cowardice by blaming aikido now.