This would be an epic battle no matter how I look at it. Hinami with her Tenseigan Chakra mode and Ria with her newly acquired Vector manipulation.
Vector manipulation may sound OP as hell but I'm not worried about it yet as Ria would at most still be at the elementary level of it.
In vector manipulation, the user can manipulate vectors of matter and energy. Vectors are quantities that possess both direction and magnitude.
Vectors are present in everyday operations; for example, a vector can be explained by an arrow. The arrow starts from point x and is now going to point y; that is direction.
The amount or length of space to travel to the second point is magnitude. In physics, the three primary vectors are position, velocity, and force.
Position is the location and orientation of something, while velocity is its speed and trajectory. Forces are the strength and direction of their acceleration, and most objects and their interactions can be described using vectors.
However, the user requires enhanced intelligence and calculation to determine what vectors affect what force. This is where my confidence lies.
Although Ria is smart, she isn't one to settle down and study. Calculation isn't her forte at all.
Examples of vector manipulation, The user can generate an aversion field surrounding them that deflects or reflects any hazardous material away by manipulating their vectors to another location.
They can control positional vectors to change the orientation of targets or induce teleportation of matter and energy, effectually attaining a valuable form of transportation.
The user can manipulate gravitational fields by using their direction (attracting to) and magnitude (gravitational field's strength) of anything, making everything weightless or weighing thousands of tons.
Augment one's physical and mental condition to perform beyond what the user is generally proficient of. The user can manipulate anything that contains a vector, from the air, kinetic energy, fire, water, down below a molecular level where atoms, protons, neutrons, electrons, and elementary particles exist, achieving a form of matter manipulation.
With vector manipulation, the user can manipulate elemental and physical phenomena to manipulate the laws of physics.
The user can potentially manipulate metaphysical vectors ranging from extradimensional forces, dreams, entropy, universes, and aspects of reality because everything possesses a vector that allows interactions to happen.
This is an amazing ability. She can even reach the state of having all the abilities of the Rinnengan, that is, the Shinra Tensei and Chibaku Tensei.
Hinami also has her own OPness to her. With her Tenseigan Chakra mode, she could use the Silver Wheel Reincarnation Explosion, Golden Wheel Reincarnation Explosion and The Casual one.
These were all used by Toneri, I haven't seen Hamuira fight so I wouldn't know, but from the battle between Naruto and Toneri, I could infer that with a little direction from me, she could master it all.
It almost seems like this was predestined with her Affinity to Explosions Release.
"Alright now, no holding back, come at me however you want." I said.
Hinami and Ria prepared to engage before Kavuya interrupted and said, "Aren't there any rules to the fight?"
"Hmm? What do you have in mind?" I asked.
"Well, as this is your dimension, you already have a home advantage, how about we give you a handicap," Kaguya said.
"Oh? Go ahead then,"
"Good, for this fight, you are not to use any perk from this dimension, you are not to use any space related ability and finally, you are not to use your domain expansion." Kaguya said with a smirk.
My face fell as she said that. I was okay with the first two handicaps but what's with the last one? That's basically asking me to lose. This is the Tenseigan and Vector Manipulation we're talking about here.
"Isn't that a little too much?" I asked.
"Not at all, you're strong as it is now, at the very least I want to see you struggle. Don't you want to bring out the best in them?" Kaguya said, adopting a tone of someone saying something for the 'greater good'.
"That's true. Shun is already pretty strong, if we fight in his domain we may lose without even knowing how." Ria said.
"But you both got an upgrade, and from what I'm seeing, the upgrade isn't small in the very least," I said in exasperation.
"Hai. Hai, how about we do this, Shun doesn't use the first two but if he uses the third, that shows we win, but we will still continue. How about that?" Hinami said in a bid to satisfy both parties.
"That's still an enormous handicap, you know," I murmured.
"Ohya~, don't tell me you aren't assured of your win, Shun. With all the abilities you've amalgamated for so long, how long is it now, 30 years?" Kaguya said in a teasing tone.
"Alright. Alright, you win, let's fight it out. Enough with the talk. You both ready?" I asked to which they nodded and I said, "Kaguya, be the judge of the match"
Kaguya nodded and formed a gun, don't know how she did that and I don't care.
"At the sound of this gun, you begin," Kaguya said and looked at me, I nodded, and she then looked at the girls, they too nodded and then...
PA!
At the sound of the gun, Shun took a step and appeared in between the two girls and punched out.
Boom
The force behind the punch took the girls unawares but they still reacted and took a defensive stance.
Hinami instantly enter her chakra mode and used a truth orb to block the punch while Ria used the sand under her feet to form a wall.
The force still pushed them back and they looked at Shun incredulously.
"I thought we agreed on no space techniques?" Ria asked with an unpleasant look on her face.
"Of course we did, but this isn't a space technique, it's pure speed. I created this technique while you both were enjoying your beauty sleep earlier. Kaguya can vouch for that." Shun said with a smirk on his face.
They looked at Kaguya who nodded in acknowledgement and then looked at Shun with an unpleasant look in their eyes.
Hinami recovered quick and said, "It doesn't matter though, let's continue, be careful though this is a new technique I just learned coincidentally and it goes well with my explosion release. Be careful now."
Saying this, she pulled on a truth orb and began infusing chakra into it.
Shun, seeing this narrated his eyes as he understood what she was about to do. That was the Golden Wheel explosion.
As Shun was paying attention to what Hinami was doing, his senses momentarily lost Ria who noticed this and moved farther away from him.
From the distance, she waved her hands and a tsunami of black sand rose from the ground.
'How the hell did she change it to black?' was what was on Shun's mind as he saw this.
The sands took the shape of various weapon and pointed toward Shun, with another wave of her hand, they all raineddown on Shun.
Meanwhile, Hinami had completed her GOE and also fired it at Shun. 'what the hell is this, I thought we were a happily married family?' Shun thought as he used the flash step to avoid the attacks.
Hinami and Ria could now see his movement as they both were already expecting it and zoned in on him wherever he went to.
Shun seeing this, increased the speed of his flash step and began leaving after images with every step he takes.
This finally got the two confused for a moment before Hinami and Ria looked at each other and smiled.
Shun got a bad feeling from this smile and became extra vigilant.
The girls nodded and immediately, several of their clones appeared beside them.
Hinami's clones all had their chakra cloaks on with the exception being that they didn't have the truth orbs. Ria's however didn't need any of that as they all could use the magnet release.
Shun finally looked grim as he didn't expect this even in his imagination.
All Hinami's clones began condensing green-coloured chakra on their palms while Ria's clones all turned to dust and filled the air around them. The real Ria though was floating high up in the air.
"You girls really are something." Shun muttered under his breath as he kept avoiding the sand formed projectiles.
"Guess I should up this a little so they don't take me for granted."
Saying this, Shun increased his speed, but the difference was that with every step, a new Shun was formed. Subsequently, all the afterimages becames various clones of Shun.
Unluckily, as Shun finished dodging the projectiles, Hinami and her clones had also finished amassing chakra, and with a shout, they all fired them at Shun's clones.
"What's this? Not even giving me a breathing space." Shun said as he and his clones dived in head first toward the incoming chakra bullet imbued with explosion effect.