The story is rushed on how he becomes "the best" with a really pathetic gimmick to gain power. I just finished episode 5.5 (yes 5.5, a recap episode and the most recent as of writing this) where it told us exactly what we just watched like it's been running for over 100 episodes. Why? The manga is rated highly, so why mess up badly on this?
The show (so far) has shown next to nothing of the side characters all the while the main and the loli (very epic) traverse the cave with horrible CGI enemies that they defeat very easily giving ZERO satisfaction. This show would much rather give me two scene of the main dude and the loli kissing, the dude and the loli bathing together, and a fucking recap episode instead of actual (interesting) story or side character back story. 0/10. Do not watch
