After the day Ren heard the truth from his mother Kaguya, he started thinking what to do to protect his mother and his two brothers. He knows from the original that his mother Kaguya was driven to eat the 'Chakra Fruit' when Land of That attacked his mother and she had to kill them for self-protection. This gave them a ploy to force Tenji to surrender Kaguya or Land of That will attack Land of Ancestor.
Tenji forced under pressure decided to attack Kaguya. But Aino helped Kaguya escape to the Divine Tree(God Tree) for protection. They know that people feared the tree and they won't go near them. Kaguya resisted the constant urge to eat the fruit and went near the tree with Aino. But they were attacked midway. Aino sacrificed herself by shielding Kaguya from incoming arrows but she was shot. Kaguya in rage gave in to temptation and ate the chakra fruit. She awakened her Rinne Sharingan and started the 'Infinite Tsukuyomi' spell binding everyone and started transforming them into Zetsu army.
As she had eaten an unripe 'Chakra Fruit', she become unstable and became emotionless, power hungry 'Rabbit Goddess'.
So to avoid the tragic fate of her mother, Ren started training under the guidance of her mother. Kaguya explained him the true power of Otsutsuki bloodline.
"Listen Ren, our bloodline is one of the most powerful bloodline. It has an endless possibility of evolution. That means for every member of our clan, their evolution may be different according to their practice. Our power mostly comes from our eyes. Also our eyes signifies the strength of our clansman. The most common feature of our clansmen is our Byakugan. Every member has them. It allows us to see the Chakra pathways, have a near-360º field of vision around ourselves, save for a small blindspot at the back of the neck. Byakugan can penetrate almost any object, allowing users to see through walls, peer underground, or even examine the contents of a person's body; only certain barriers have been shown to block a Byakugan's sight. The exact range of the Byakugan varies between users, but can be improved with training. Its ability to see chakra is acute enough to see the chakra pathway system within a target's body and the 361 tenketsu that run along it."
"Ren, my Byakugan could emit pulses of chakra to subdue targets. I analyse an opponent's tactics during a fight, granting them a certain amount of predictive ability. The most advanced Byakugan allows to see into a target's mind to determine their thoughts and feelings, even to look through their memories. Lastly it can determine the development of one's chakra. When Byakugan is active, pupils become more distinct and the increased blood flow to their eyes causes the veins near their temples to bulge."
When Ren heard her explanation, he was astonished to hear that byakugan was so powerful. No wonder it was compared as equal with Sharingan in the anime. Hyugas bloodline must have been diluted or they lost their inheritance. As for the evolution of Byakugan to Tenseigan, he has to ask his mother.
"Mother, you said that our bloodline could evolve. So, can our Byakugan be evolved?" Ren asked his mother to which his mother, smiled.
"You are intelligent and good listener, son. Yes our Byakugan can evolve to many different forms. It depend upon your nature of chakra. You know that our power comes from chakra. But chakra has 7 different nature. This is basis of all creation in the universe. These are the 5 elements 'Wind, Water, Lightning, Fire, Earth' and the most important 'Yin-Yang'. You can find 5 elements around us. But 'Yin-Yang' is different. This is the most difficult nature transformation. If you mastered it to the pinnacle, you can overcome the limit of mortal, become immortal."
Ren gasped when he listen to the secrets of immortality.
"These are all high level practise. Even I am unable to do. Your father almost mastered them. I am just starting to learn. Before I didn't get time to learn them. After war started, I have to be on constant lookout. Then I was pregnant, my power diminished to the minimum. The practise of 7 nature takes a lot of time. So ordinary clansmen cannot complete their mastery before their lifespan ended. So many clansmen seeked for chakra fruits. One. They allows our Byakugan to forcefully evolve which in terms helps in practise. So many of our clansmen succumb to greed."
Now, Ren finally understand why Momoshiki or Urashiki were downfallen that they even ate their clansmen as chakra fruit. The temptation of increasing lifespan and evolution of Byakugan is indeed somewhat unbearable. Even Ren is now tempted to pluck the chakra fruit and eat it.
Kaguya who was keeping an eye on Ren saw the conflict in his eyes. She shouted
"Ren! Don't even think about it. I know that temptation. Many have fallen. You must bear with it. If you walk this path, returning is very difficult. Practise hard. Don't make your father and me regret the decision."
Ren broke out in a cold sweat. He suddenly feel dangerous towards his thoughts. He absolutely cannot make his parents disappointed. He will not get a chance to regret again.
"Thank you mother for waking me from my thoughts."
"Bear with it Ren. Only this way you can reach the top. There is no shortcut for immortality."
"I understand mother. I keep your in my mind."
"Worthy of our son. You can realise your mistakes and make amends, you can someday reach immortality."
Yes why should he think about shortcuts. With his IQ, he can find other ways to immortality. There must be other ways he just had to find it. Orochimaru dedicated his life to it and finally he achieved it in some ways though not perfect. Now he had to find out how to evolve Byakugan or how to unlock the most powerful Rinne Sharingan!
"Mother you didn't tell me how to evolve Byakugan."
"Well Ren, listen carefully. Evolution of Byakugan is mainly due to some mutation of bloodline which allows some special abilities to both our eyes. Sometimes extreme emotion also help in evolving of Byakugan. You can know by looking at the color of Byakugan."