The Tower's Sole Regressor

After losing his beloved, Rin fell into a deep depression. Still, encouraged by his brother-in-arms Jack, the two challenged the Tower's 90th Floor. But, upon entering it, they realized that they were far from ready. As Rin stood helplessly, his companion was slaughtered by a mysterious and powerful Being. [A certain Outer God is manifesting the full extent of its Authority.] A second chance came knocking. A chance to rewind time. What choices will Rin make? What does he wish to accomplish with this second chance? Can he make it to the top of the hundred leveled Tower?