To say that the scene in front of Ren was chaotic was an understatement, jets of water, sparks of lighting, kunai clashing, and shuriken flying everywhere, and in the middle of this chaos were, Chojuro, Dosu, Haku, Ao and him, evading the endless stream of attack trying to find a moment to counterattack.
As Ren evaded another jet of water, and sparks of lightning he heard Ao's voice that said "Guy! This can't go on, I'll take care of the defense! As soon as I'm done go on the attack, but remember to conserve your energy as much as possible" the he started doing the hand seals very fast as a new series of attack was coming from all the direction.
As soon as he was done he said "Suiton: Suishōha (Water Release: Water Colliding Wave)" and creates a massive vortex of water that protects them from attacks, it explodes from the top of it in the form of a wave, covering the entire battlefield.
By using hand gestures, Ao manipulate the water to move in the direction of all the ANBU around them.
Having changed the battlefield in this way enables Chojuro and Haku to follow-up with additional Water Release techniques, which they do as soon as the jutsu ended and the attack from the ANBU momentary stopped.
Chojuro use the Suiton: Suisō (Water Release: Water Spikes) and produces large spikes capable of impaling clean through a target, this technique can be performed from afar through any existing water source, even mist, to rain down on its foe or erupt from the ground.
But Chojuro jutsu was only used to force the ANBU to evade and divide themself even further, while at the same time Haku used Sensatsu Suishō (Thousand Flying Water Needles of Death), and creates a thousand long needles from the nearby water, which surround the targets.
Haku carefully aims the needles at the targets and fires them at rapid speeds, and the targets who are struck by the needles suffer significant injury in all non-lethal areas who slow the majority down while 3 of the 23 ANBU are unable to fight any longer.
Meanwhile Dosu took advantage of Chojuro jutsu and moved toward the largest cluster of enemies ninja, once there he started hitting one after another with one Kyōmeisen (Resonating Echo Drill) after another using both arms causing all the hit ANBU around him ,and the sound damages his target's semicircular canals, throwing them off-balance so that they can't stand, move, or fight.
And so another 5 of the 20 remaining standing ANBU are down for good all around Dosu as some are left dizzy, with distorted vision, and vomiting, but as Dosu was making sure that they won't get up again, he heard Ren's yells "Dosu! Watch out! Back!".
And so hearing his warming Dosu turned and saw a jets of water moving fast towards him, and then was able to sidestep and evade said attack, but as the jets of water was still going, Dosu quickly swung his arm through the water sending another Kyōmeisen across the water, right into the attacking ANBU mouth knocking him out with bleeding ears.
As this was going on, in the background Haku and Chojuro combo knocked down another 4 ANBU using Haku's senbon together with Chojuro's kenjutsu cutting their number to 15, while Ao was using water release to defend and support them, while also hindering the opponents.
Meanwhile Ren was clashing his sword with 5 other ANBU who choose to use close combat as he was parrying and evading the various attack he thought 'Never thought that not killing an opponent was so much harder than killing them, well better move' and so as he parried another attack from the 3 ANBU in front how him.
He chanted as he was still clashing with those 3 swords "Hadō #11. Tsuzuri Raiden (Bound Lightning)" that generates an electric current through Senbonzakura, which damages anything and anyone which is in contact with it, in this case the tree swords and ANBU who once struck by it get knocked down.
But as this was happening Ren pointed at his back, where the other 2 ANBU took the chance to strike him and chanted "Bakudō #8. Seki (Repulsion)" and generates an orb of light blue energy which repels whatever strikes it and then turns around and hit one of them with his fist in the stomach "Ikkotsu (Single Bone)".
A powerful punch which can destroy much of the target's abdomen, send the ANBU flying along many trees, until he hit a big stone and remains struck there, unknown if dead or alive, and at the same time a senbon from Haku hit the other in the neck sending him in a state of unconsciousness.
Then Haku appeared near Ren and seeing the result of Ren's blow said "You know that, if possible, we have to spare them right?" and as Ren knocked out another 2 ANBU hitting them in the neck with the back of his Zanpakuto, he replied "He is alive, maybe he will need 2 month of hospital but he is alive...." then in a low voice he said "....I think"
Meanwhile Chojuro and Dosu lower the number even more and now there are only 10 ANBU remaining and now that the number advantage was gone, Ao stopped focusing on supporting his teammates, and started going on the offensive, knocking out one ANBU with a Suiton: Suidan no Jutsu (Water Release: Water Bullet Technique) and choking another that was about to release another jutsu at Chojuro from behind.
While Dosu and Haku did their first combo play, with Haku using Hyoton: Tōdo (Ice Release: Frozen Ground) putting the hand on the water to create the surface of ice, and froze the remaining 8 ANBU's feet, while Dosu slammed both his arms in the frozen ground sending a Kyōmeisen across it, and fun fact the sound in the ice move faster than in air or water, so the ANBU didn't have even the time to free themselves and were all knocked down.
As soon as they finished Ren and the other made sure that all the ANBU were out of combat and unable to support Yagura, but as they were doing so the felt a huge malicious chakra and a powerful roars, and from afar they could see the huge figure of the Sanbi.
Then Ao said "Ok listen! Now we separate, Haku and Dosu go and support Zabuza, meanwhile I, Ren and Chojuro, will go and help Mei, clear?" and everybody respond with a "Yes!" and went toward their targets.