After his first meeting with Itachi, Ren took Peri and used once again the Bakudō #87. Sentan Hakuja (Thousand-Coil White Snake), and teleported to his hidden training ground in the Land of Water, that is a carbon copy of the one near Konoha, Ren during his journey this one year created one hidden training ground for all the main country.
'Now I only have to wait, but this time it is better that I go alone, I do not know why but I feel that this time too it will be a combative negotiate' then Ren prepared dinner and after that he started meditating.
For the next week the days passed the same way while he waited for Itachi to contact him, meanwhile he got news from the others member 'Dosu, Zabuza and Haku finished their job too and were able to find some info on some of Orochimaru hideout, were the syndicate send the majority of the test subject'.
As Ren was reading the report he felt the Jigokucho in Itachi scroll's call, so Ren turn to the swimming Peri and says "I'm going to try to convince the bro-con to not kill himself" and Peri just gave him a thumb up, then Ren used the Bakudō #87. Sentan Hakuja and teleported near the coordinate given by the Jigokucho.
Once there the first thing that Ren noticed is that it was raining then he look around and find the place somewhat familiar, and in the distance he could see a terraced mountain with vast forestry growing on each level, two towers were also built on either side of the mountain connecting directly to it.
'Where did I see this?....Aha this is the Uchiha Hideout, where Itachi and Sasuke will fight, does he like this place so much?' then as he moved closer to the mountain he could see at its base the figure of Itachi, waiting for him.
"So what do you say, do you want to join my group?" and Itachi looked at Ren in the eyes and activated his Sharingan, and as soon as he did so he felt Senbonzakura jolting his chakra, and breaking out of the genjutsu so he says once again "Sorry but genjutsu doesn't work on me..." but before he could continue Itachi says "Also your genjutsu won't work here, I already noticed that your genjutsu work on smell, and in this torrential rain it will be quickly washed away"
Hearing that Ren starts slowly clapping "Bravo! It took only one encounter to notice that, but why doing this? All I asked is for you to listen to my plan to save you and Sasuke from your stupid plan" and Itachi "And before I listen to your plan, I want to know if you got the strength to change the events in motion"
Then Itachi creates two clones with the Kagebushin no Jutsu (Shadow Clone Technique) and sends a volley of shuriken towards Ren who draws Senbonzakura and starts deflecting them, meanwhile the clone of Itachi went to the sides of Ren and used the Suiton: Suiryūdan no Jutsu (Water Release: Water Dragon Bullet Technique) moulding the falling rain into the shape of a dragon, which they then direct at Ren in a pincer attack.
Ren retreat using a Shunpo evading the clash between the 2 water dragon and then he says "Why the hell everybody keep using Water jutsu against me!? Is it the most common element in this world? and you are a fucking Uchiha use Fire for the love of Kaguya!" but as Ren was running his mouth 2 other clones appear behind him and once they were close enough, they detonates, creating a very large explosion.
Then from the cloud of smoke created by the explosion the figure of Ren is seen bolting out, and even if he is a little worse for wear he isn't injured, as he at the last second remembered that Itachi often used the Bunshin Daibakuha (Clone Great Explosion) and so he turned to the two coming clones and using his Zanpakuto in a blocking motion he said "Bakudō #39. Enkōsen (Round Lock Fan)", generating a dull yellow energy, which takes the form of a large spinning disk of condensed Chakra, in front of himself, blocking the majority of the blast.
As Ren got out of smoke cloud he is once again assaulted by 3 Suiton: Suiryūdan no Jutsu coming from Itachi and his 2 clones, and Ren annoyed by this points his palm at the coming attack, discharges blue flames from it and says "Hadō #33. Sōkatsui (Blue Fire, Crash Down)" and generates a torrent of blue energy before firing it, and it move like a large wave of energy, that engulfed the 3 water dragons and also Itachi and his clones.
But Ren then look at his left and says "So...what do you think? Is this enough?" and from the bushes walk out the figure of Itachi that replies "Yeah, for a warm up is enough, but if this is all you can do, I prefer to stick with my plan".
Hearing that Ren raise Senbonzakura in front of his face and says "Then I'll raise the bar, Chire (Scatter), Senbonzakura", and under the carefull gaze of Itachi his blade scatter in a thousand of petal-like blades.
And Itachi sensing the danger decide to use one of his most proficient jutsu, kneads chakra in his body and turns it into fire, which he then expel from their mouth "Katon: Gōkakyū no Jutsu (Fire Release: Great Fireball Technique)" in the form of a giant orb of fire, meanwhile Ren thrust his handle and send a torrent of petal-like blades toward the coming giant orb of fire.
And in the next instant both attack clash and the orb of fire explode, raising a lot of smoke and creating a big crater, but Itachi who just fininshed using the jutsu, notice some movement from the smoke, and then he saw the torrent of petal-like blades coming at fast speed, too fast for him to evade.
Then as the blades move closer and closer to Itachi, his Sharingan starts to change and it design become three spiralling curves around the pupil, then a bright red ribcage arm and a skull formed around Itachi, but Itachi felt that this wasn't enough and next musculature and, later, skin forms until finally a complete humanoid is shaped.
And then Senbonzakura clash against the red humanoid figure, but is unable to fully damage it as it leave only some scratch, but even that surprised Itachi who says "Oh....Not only you forced me to use Susanoo up to the second stage, but you were even able to lightly damage it, and that sword of your is really peculiar it scattered in a thousand of small pieces but didn't lose sharpness or toughness as even my Katon: Gōkakyū no Jutsu didn't do anything...well let's see how you fare against this....".
And Ren who understand what Itachi is about to do, swing upward his handle and Senbonzakura form a wall of cherry blossom petal-like blades in front of himself, and the next instant said wall is engulfed by the black flames of Amaterasu, that while they keep burning on Senbonzakura are unable to damage it.
Itachi seeing that says "Really tough...then brute force it is" and he put out Amaterasu's flames and once again concentrate on Susanoo, and soon also the armor starts forming, and in the end Itachi's Susanoo resembles a long-nosed tengu that possesses a curved blade that resembles a dagger or tantō on its waist, on its primary right hand and sheathed in a sake jar held by its second right hand is The Sword of Totsuka, and in its primary left hand wields the Yata Mirror, a shield that can change its nature depending on the attack it receives, thus nullifying it.
Ren does not wait anymore and send another attack but Itachi stay still and let the attack hit the armored form of Susanoo, and see the it's ineffective and so he says to Ren "This is the ultimate jutsu of the Uchiha clan, Susanoo, the perfect defense and offense, as you can see even your strange blade cannot do anything against it".
Ren hearing that re-seal Senbonzakura and pointing his palm at Itachi use once again the Hadō #33. Sōkatsui, but Itachi use the Yata Mirror to nullify this attack, and says "It's useless give up, you can't win, I'll let you go..." but before he could continue he notice Ren smiling.
Ren took Senbonzakura and pointed downward toward the ground and said "I can finally use it....you have no idea how long we waited for this moment....Thanks for begin so strong!" the Ren with a big and confident smile, and under the curious gaze of Itachi, drops his sword straight down and as the sword is falling he says "Bankai!".