How could I beat chapter 9?

First, Equip 3 scrolls from the list to everyone:

Book of Attacks Lv. 4
Way of the Ninja Lv. 12
Hidden Dream Tome Lv. 3
Hidden Dream Tome Lv. 4
Null Lethal Poison Lv. 4
Null Flexible Lv. 4
Null Sluggish Lv. 3
Null Heavy Sluggish Lv. 4
Null Seal Lv. 3
Null Complete Seal Lv. 4
Null Paralysis Lv. 4
Null Paralysis Lv. 3

(NOTE: Try raising your Attack power close to 400 or more for everyone)

The main Status conditions that happen in this Battle are Flexible(defense goes down), Paralysis, Sluggish/Heavy Sluggish, Chakra lowered, and Attack Power lowered. Try getting rid of the rouge Ninja first, so you won't get Surrounded(Don't worry, they aren't endless), and When Fighting Enzo, Wait for him to attack, then Substitute Behind him and pummel him with Short Combos, as well as Assist Attacks. He should go down quite easily.

When he transforms into his Beast-Man Form, He fights Exactly like Ryuka. Like your fight with Ryuka. Wait for him to attack, then Substitute Behind him, and pummel him with Short Combos, as well as Assist Attacks. When the Rouge Hidden Dream ninja attack, try ignoring them, but if you can't, then use short Combos to get them out of your way. Again the Rouge Hidden Dream Ninja aren't endless. Also, there's a 4 trees, and a boulder you can break to raise your Kizuna points as well.

Hope this makes beating Enzo a little easier for you.

To add onto the answer above, you should first focus on the enemies, then on enzo. That will make him an easier target. Hop that helps too.