Some things I usually make space to bring.
Toothpaste with flouride.
Contact lens solution and eye drops (solution can be really expensive and I just like my brand of eye drops too much)
Cold meds not restricted by customs (Sudafed is restricted, last time I checked. Japanese cold medicines just don't do it for me. Some even make me feel worse!).
Deodorant. What they say is true for me. Japanese deodorant doesn't cut it.
Sun block - they have it here, but in small bottles for a lot of money.
Over the counter allergy meds.
Things dealing with the gut, intestines, and the stuff produced therein. When I am sick, I like to go with what I know.
I have yet to find a thing that hold a candle to Sucrets[sic?] for sore throats in Japan.
Take some stuff in you bags and then sea-mail yourself a big box of things you like. You will probably end up spending less money for the same types of things and you will know that they will work for you. Enjoy your trip!