After Shie Hassaikai, Ryuko tends to herself mostly at UA. However she did not participate in the School Festival, as she finds it "Too crowded for my own good".
However as she glided through the skies of Musutafu in her transformed state, she witnessed Izuku fighting off a villain named Gentle. Beside them is a little girl who is cheering on Gentle.
"You've picked the wrong prey today, Aiba Manami... Also known as La Brava."
Ryuko's voice echoed through the forest, as the skies turned black and white rocks and other surfaces around Izuku, La Brava and Gentle begins to emit a strange glow.
"T...This is...!? Moeru!?"
"Moeru? Who's that--"
La Brava is then silenced as she looked down to see a black claw protruding from her stomach. No blood came out, but the claw emits a red streak of electricity.
Suddenly the trees and the air surrounding the area stopped being elastic after being manipulated by Gentle.
Gentle, with a surprised look turned around to see Ryuko. La Brava is then let go, and she collapsed to the dirt below her.
"What a shame. Your lover cheering you up like one would to their favorite gladiator, now down on the dirt like the trash she is... Tobita Danjuro, also known as Gentle Criminal."
"You...! Just, who are you supposed to be?"
Ryuko didn't answer. Instead she just spat her oil at Gentle, soaking him. And in an inhuman speed she whizzed towards him, and blew out a small spark of fire, which then engulfs Gentle up in flames in front of La Brava. Thanks to him wearing rather defenseless clothes, and the wide cape, he was an easy target to burn.
"NO!"
"If you want him to live, beg."
Gentle's screams are filling the forest, as he then tried to extinguish it by rolling around the ground.
"You... You aren't a hero at all...! This is inhumane!"
"You should've thought about your actions earlier. Should you used your quirks to help others... Just like what Gentle wanted before he became a villain, then this won't happen. Now beg, if you want him to live."
"F...Fine! We admit our errors! Please save him!"
"As promised."
Ryuko then breathed out a mist of ice, which then extinguishes the flames, however freezing Gentle in place, just as the pros arrived.
"He's all yours, Sensei."
Ryuko then flew away. She does nothing much for the next few days other than studying, training with classmates, as well as observing Izuku. However later on, after the Hero Billboard Chart event Ryuko called in sick, which is odd as Ryuko never contracted any diseases before.
Aizawa tried to refuse, but Midnight came into the classroom at the same time, only to say that she is allowed to leave. Immediately, she undressed as her armor forms around her, transforming her into her dragon girl form. She then flew out of the window, faking signs of being sick by flying shakily. She disappears within a sea of clouds.
"Why'd you let her leave?"
"Because something is up whenever the Alatreon made up her mind, Aizawa. Also, if you want to sacrifice Amajiki that badly to her, then go ahead."
She said that since that day, 1-A would be sparring with Nejire and Tamaki. At least the latter is spared from the fate of being possibly burned alive by Ryuko.
As for The Blazing Twilight herself, she flew back normally, as she sets her course towards Central Fukuoka, where she sees Endeavor and Hawks, the Number 1 & 2 Heroes respectively fighting off a persistent Nomu. Both are heavily fatigued, as no matter what they did, the Nomu would just regenerate.
The Nomu, named Hood chuckles, as it says "Weak... Give me a strong hero!"
As he took one more step, the skies turned black, surprising everyone except for the Nomus.
"T...This is..." Hawks gulped after those words.
Hood is then suddenly engulfed in flames, before shaking them off as his burns then healed themselves. He looked up, to see Ryuko plunging down at him.
"Oh."
And a loud thud is heard, as Ryuko smashes him to the ground, creating a crater out of the ground beneath them.
"It is a shame to see the new number 1 and 2 heroes are being manhandled by a single abomination."
"Alatreon...!" Endeavor said between gritted teeth.
"Let me handle him, Todoroki Enji, also known as Endeavor."
"Good luck with that. He's fast AND tough."
"Ara~? We'll see then."
Ryuko then turns around to face Hood, who mumbles.
"New prey... Seems strong."
The both of them walked towards each other, and they traded blows. However, Ryuko manages to sway her hip to the left to evade his right hook, as she did an uppercut to his chin, sending him flying upwards.
"Fool... I can recover... What? Jets... Not functioning..."
In the air, Ryuko flew upwards following Hood, before she spun around, whipping him with her tail three times, with the third time being so strong that she sends him flying away. She then flew as fast as she could in front of Hood, before backhanding him, cracking his teeth.
"What...? Why can't I... Heal...?"
"Dragonblight, Sonny."
"Who's sonn-"
Suddenly, Ryuko wraps her arms around Hood's body.
"W...What is this...?"
"You're not even worth the effort..."
Suddenly the clouds around them begin to rain out hails of falling ice as the air is filled with freezing mists. All sounds are muffled down, as Thunderbolts and dragon bolts begin to strike the both of them, before Ryuko chanted her ultimate move.
"Escaton... Judgement~"
And what happens is the skies are filled with thunder claps and explosions.
In the explosion, the Nomu Hood felt his body being disintegrated into ashes in a flash.
"Is this... My end...? Too... Strong..."
When the explosion fades away, Ryuko, in her Ice Active form, makes a sinister grin as she sees the dust of what was once Hood flying into the air, disintegrating atom by atom as she then breathed out a jet of flames at them.
She then flew back down, and pushed both Endeavor and Hawks to the crater she made earlier, before flying away.
"E-Endeavor won! The Number 1 Hero has finally defeated the villain!" A civilian shouted.
Endeavor and Hawks took credit of the victory. However Hawks is too shaky when he appeals in front of the others because of the truth he witnessed. Even he doesn't know wether to put Ryuko as a friend or foe.
As for Ryuko herself, she flew back to her apartment to rest as she lived away from UA. Nobody dares to invade her anyways.
"I took care of such nuisance just for you Midoriya-Kun. Now that's one less trash that you need to take out... Because I'll do anything for you, so that you won't have to face such overpowered opponents... That might kill you."
She said, as she glanced at the photo of Izuku.
"As there is no other symbol of peace... No, hope... besides you."
She then looked at her wardrobe mirror, seeing her face in the reflection. Her eyes then start to glow violently.
"...If you did die... Then I have to destroy this world."