Kurenai had learned a lot from Anko's demonstration. Originally, she planned to just seal the curse mark with the evil sealing method. It was a technique that relied purely upon the will of the user to suppress the cursed seal's effects. As a general counter method its applications were numerous against Juinjutsu.
As long as the user willed it, they could not be affected by the enemy's activation of the curse mark. It would prevent the normal pain that was associated with the curse as well as stopping its activation. This technique was originally designed in secret by Shimura Danzo, the Leader of Root and Advisor to the Hokage, in order to suppress the caged bird seal. The Hyuuga branch members within root would be controlled by him alone.
Since it relied upon the will of the user, it could not prevent the Juinjutsu's activation after death. This mostly kept the Hyuuga's ire at bay while also satisfying Danzo's interests. However, it could only be legally applied to suppress the Caged Bird Seal if the branch clan member was joining root. Otherwise it would encroach on the Hyuuga clan's authority.
Orochimaru's cursed seal had no such restrictions in place. She was free to restrict it however she pleased. However...
"His Cursed Seal... It's not so simple. It also seems to have a component of influence."
Anko's demonstration and insights were extremely beneficial to the current Kurenai. She was grateful to Saul for his prudence. Whether he knew it or not, his insistence towards getting the reluctant Anko to show the cursed seal was immensely helpful.
Hinata frowned and trembled while unconscious. Kurenai heard applying the evil sealing method was immensely painful - she was glad the girl wasn't awake to truly experience it.
"Hinata bear with me a little longer. I still need to take this a step further."
Her hand, radiating with the light of the mind body palm, clasped onto the marking on top of Hinata's skin. Kurenai closed her eyes.
The world around her shattered as she entered into a Genjutsu world of the consciousness within. Water was spread all along the floor as the full moon shone overhead. A pale faced man, with purple spikes of face paint, sat at a table in the middle of nowhere.
"Welcome... Come, have a seat."
Kurenai remained staring, watching him with disgust.
"You attacked my Genin."
"I'm sorry, did I scare you?" Orochimaru licked his lips. "I was merely playing around. I didn't seriously harm the cute little Genin."
Even now, the snake bastard played innocent. He had ruined the lives of so many people, her friend, and now Hinata's. Yet he never acknowledged any fault! Kurenai was speechless.
"...Get out. GET OUT! You better leave her body before I force you out myself!"
Orochimaru chuckled. "Are you sure you want that, young Lady?"
The man got up. His footsteps created ripples in the water below as he moved, disrupting the reflection of the Moon below. The man looked like a demon within the night. ʀᴇᴀᴅ ʟᴀᴛᴇsᴛ ᴄʜᴀᴘᴛᴇʀs ᴀᴛ noⅴelfire.net
"You see... This 'gift' of mine is part of the fun. This is only a small fraction of my consciousness. If you really wanted to, I'm afraid I'd truly be erased. But."
He leaned in closer, licking Kurenai's neck. She reeled back with disgust. Orochimaru's tone went flat, losing all of its playful amusement.
"It wouldn't be all fun and games anymore, would it? Remove me from the seal, and I'll know. The first ones to suffer from the consequences will be the ones you care about. What was his name...? Sarutobi Asuma, was it?"
Kurenai went pale. "You wouldn't."
Orochimaru chuckled. "I still remember you two, mere children on the battlefield I commanded. Asuma came to me continually begging for me to assign you the safest missions, you know? He was the Third Hokage's son after all. I had to take great care of you from behind the scenes."
What? Asuma did...? But that was corruption, wasn't it?
"No... You're lying!"
Orochimaru licked his lips, "My dear, why would I lie to you about such a thing?" He stepped back and sat onto the chair he offered Kurenai. "You see, I wish to take that little white eyed bird under my wing. Before she is caged by the abominable Hyuuga. I wouldn't kill anyone she cares about, so do not worry. Your life is safe."
Kurenai felt a sense of disgust towards Asuma and guilt at the revelation. She hadn't just gotten lucky, no. It was all due to her childhood friend, Asuma. She should have been one of the casualties. People had been sent to die, so she could live. What had Asuma been thinking!? Did he believe she would be ok with something like that!?
"I should have expected no less from someone like you. It's no wonder you were not even selected as a candidate for Hokage."
Orochimaru sneered. "You think I actually care about something as meaningless as that? Erase me from the seal, and you'll see what happens. Within this decaying, dying old village, no one can even think about stopping me. Especially not that dying old fart you all still call Hokage. I've surpassed him long ago."
He leaned forward. "So, what's your move? Shall I stop playing around?"
Kurenai vanished without another word, trying her best to contain her rage.
"Hahaha. Hahaha! HAHAHAHAHA!!!"
Orochimaru's mad laughter echoed throughout the empty space.
The red eyed woman's eyes blazed with rage and fury. She looked down at her poor, unconscious student, and frowned. She had to help her no matter what. But how...? Ah. She could do that.
A cold faced Kurenai formed hand seals for the Spirit Cleansing method. Sure, if that bastard wanted to keep playing he could play all he wanted. But she'd cut out his influence. No matter what, she wouldn't allow him to hurt the Ninja under her protection.
The Spirit Cleansing seal was a Genjutsu-Fuinjutsu hybrid. It predated the Evil Sealing method, designed by the Uzumaki to combat certain potent Genjutsu techniques that were inscribed onto the body directly. Said seals could never be removed without a specific counterseal, so the affected Ninja were compromised until one was developed. Until this method was created.
The seal would forcibly insert the user's will in direct opposition to the tainted will within the Juinjutsu's chakra. It allowed them to suppress the rootless will with their own, turning the corrupted chakra harmless. This would form a double layer of defense for Hinata.
The Evil Sealing method prevented the Chakra from the seal from escaping the affected area. The Spirit Cleansing seal blocked the seal creator's intent from influencing its host. Even if Hinata had to end up using the chakra from the seal, she could still fight against its corruption directly rather than being insidiously influenced by the mark itself.
"Let's see how you ... Orochimaru."
She placed her thumb directly around the compressed Fuinjutsu writing surrounding the cursed seal and started drawing. A spiral pattern resembling one of the ones found within the Four Symbols seal started to take shape. The Spirit Cleansing seal was actually one of the four symbols used - to prevent the tailed beasts from driving their hosts insane with their chakra.
Hinata's body tensed and then relaxed. It was done.
Kurenai got up to her feet. She would go find Saul and Yakumo to tell them it was done. They weren't authorized to interfere with the remaining participants. In her haste to help Hinata, she had forgotten to mention anything. She was afraid that if she left them to their own devices, they'd do something they weren't supposed to. Especially Saul. Who told him to gather that many scrolls!?
Author's Note - In the original series, both Kakashi and Kurenai used the evil sealing method. It makes much more sense however for someone like Kurenai to be better at sealing than someone like Kakashi. She is not a combat specialist at all, and she's explored alternate fields like Genjutsu so much because of that fact. They're her passion.
Also this is the little butterfly effect thing I mentioned going in Saul's favor with Kurenai on the discord :P. It makes things make much more sense on how someone like Kurenai survives the 3rd great ninja war. Maybe an AU but also a possibility in cannon idk.