Checked luggage and possible customs question?

I am soon to go overseas to live in Japan. I am also undergoing a personal project and have been for 2 years, foreskin restoration, which I'm sure will get me some interesting looks listing that here. But, I plan on bringing my equipment with me so I can continue to restore my foreskin whilst in Japan. My equipment looks strange if you are not aware of what it does, but it doesn't look harmful, for example some of the items are...an uninflated balloon attached to a plastic rod with clear plastic tubing and a plastic fish tank valve which sets airflow, a pump from a blood pressure cuff, a large metal ring which is unscrewed into two large halves, some plastic baby bottle nipple though modified with the tips removed, a long suspender strap, a velcro strap, and a soft rubber cone with a metal ring and a soft rubber ring.) I really don't want to have to explain to those checking luggage what they are, but will if necessary, nor do I want my luggage to arrive in Japan and come to find those materials were removed among my luggage. I was thinking to ship them to myself, but I'm not sure how to register these things with customs, or if it is easier and not a hassle to take them with my in checked luggage on the plane trip, I would love to know. Please give me your insights and ideas, thanks.