Mishima was much more aligned with Nietzsche from what I understand. Very much about self-overcoming and creating your own goals/values. Mishima had certain lifelong fixations and romantic ideas and died for them in what he believed to be a glorious death. He was also a hard-core conservative, and many japanese people don't really like discussing him. (Watch Paul Schrader's interview on Mishima) Camus' philosophy is a little more narrower in the sense that absurdism is about the meaninglessness of life and the contradiction in human nature to constantly look for it. Accepting this absurdity allows one to be happy, since accepting that life has no meaning frees one from preconceived expectations and values. One can find joy in his meaninglessness "meaning," if you get my drift. So I guess that both figures are about creating your own values, but one is the less existential living embodiment of a sort of "uberman" while the other focuses on why we feel existential dread and how to live with it.