Re: exiting a dojo
If you want to go, then go.
But my suggestion is to have a conversation with the Sensei first.
All you need to say is that you want to go elsewhere....and thank you for the time spent with you.
There is a lot of 'churn' running a dojo, there is a lot of competition, lots of distraction and in all honesty its a bloody tough job at times.
Not all of this is obvious to the students, most instuctors I know keep the baggage to themselves. Maybe in a conversation you maybe surprised and find out some reasons for historic behaviour....maybe not.
If you have the conversation though, you'll have done the right thing and as well as giving respect, you'll also have earned it back.