The current level cap is 85 and the 9th chapter is for the lvl 90+, so you need to wait.

err.... no, we have ch 9.
I'm not entirely sure if we can fini* (I stopped in middle of the 84 missions due to lv cap. While exp now can build up, I do not trust them fully to actually get that to work, so I'm still holding). Given the amount of stars I'm missing and the USUAL amount of instance per level thou, I'd bet on we can't fini* yet.

The reward is gakido btw, this, however, might not be possible until lv 90 cap rolls around. Once again, I dunno if we can actually finish ch 9 right now.

There is a chapter 9, they reward you with 80 Gakido pain fragments if you manage to complete it.

However, at the moment, due to level restrictions, you can't complete this chapter yet, only around half of it..maybe 3/5, I'm only 81.