I'm tattooed and going to Japan

I have small (19) black butterflies that go from my ankle to the side of my knee, and a small cross with crown of thorns on my upper spine. Should I put a bandage wrapping over my leg? And if I were to go to an osen, is there a way to keep it covered? Any advice on how to travel around Japan without offending any of the locals or my host family with my tattoos would be awesome.

The only concern for you should be the onsen, where they may not let you in. Anywhere else in Japan, you'll have no problems.

Beaches, water parks and gyms may also be a problem, but most travelers don't visit these.

My housemates in Japan used bandages or medical tape when going into places that prohibit tattoos :0

you really have a problem anyplace except of onsen. You might be able to find an onsen that will let you in, but be sure to ask and don't try to "seek in". Don't try to cover them up with bandages or whatever. Bad manners to go if your bandaged up.
(on the street) You'll find most people don't care, your a gaijin. Depending on where you go, you might see lots of people checking them out coz they don't see to many. But just depends on where you go.
Just respect the culture and understand that there is some place and things you can't do. You'll have a blast, enjoy yourself!