A giant thunder rain happened for a few seconds, Emilia and Ram only could witness such gigantic attack, in the skies, a giant beast, bigger than a house, having orange feathers, a long serpentine tail, human-like mask with big eyes and an distorted look on it's face. Said beast looked down at Ram and Emilia and then... Disappeared, like it was never there.
Not knowing what kind of monster it was, they ran faster, so they could reach Subaru and Rem, in their hurry, they noticed the various dead bodies of Majuus, scorched corpses with steam coming out of them.
As they followed the trail of dead bodies, they found out Subaru calmly holding Rem in his arms, as she slept soundly.
Subaru: Yo.
He waved at them, but before he explained himself, Ram approached quickly and took her sister from his arm
Ram: what did you do to Rem, Barusu? Did you finally noticed her beauty and tried your way with her?
Subaru: ... She tried to attack me, so i flicked her horn
He says nonchalantly, sighing a little, he went to talk with Emilia, however, he was attacked by the "Leader" of the Mabeast, the big one, he used earth attacks to try and damage Subaru with a giant rock, however, the Wielder of the Ten Shadows calmly scuffed off the attack, as if was nothing to him. It seems the creature survived Nue's lighting, it was definitely strong, however, not as strong at the Bowel Hunter, so it's nothing he couldn't take care of.
Subaru: It's a tough one
He felt the air around him start to get cold and feisty, as he noticed Emilia and Ram preparing to attack, but he interrupted them
Subaru: i can take care of this, get Rem and the children and run!
As he said, the giant Mabeast went for a bite, leaping towards Subaru with a ferocious attack to cleave Subaru in half!... However, it met a giant dark fist into his face, launching it to the left, breaking two trees in the process.
Subaru: Divine Dogs... Totality
The giant Boxer-like shikigami appeared out of Subaru's shadow, the giant was sizeable, around the same as the Mabeast, with it's giant fist, it pummelled the wild being in the face, throwing him to the left.
Afterwards, Subaru quickly unsummon's Divine Dog Totality, clapping his hands together, lifting his palms as if he was aiming with his hands, pointing at the creature and whispering
Subaru: Max Elephant - Piercing Water
A jet stream of water exploded from the tip of his hands, flying at mach speeds towards the Mabeast, piercing through its arm and body, making it whimper and growl at the boy, who just ran at it's direction, his eyes where focused, more than ever
Subaru: Koku....
He clenches his right fist, focus his cursed energy on his knuckles, jumps towards the dog and prepares a giant right hook
Subaru:SEN!
As his fist connects, Rem wakes up to an Ram and Emilia in awe, looking towards Subaru and... A Black Thunder sparking from his fist, as his punch destroys the Mabeast face and teeth, sending it flying towards some trees, breaking them down, but yet... It was still alive. Truth to be told, Subaru wasn't going all out, he was just... Experimenting things while holding back massively
Subaru: not that a beast shall understand... But this... Is true Jujutsu
He Intertexere his fingers, making a.. weird hand gesture, his shadows expands, engulfing all the area around them for about a radius of 50 meters, as a giant skeleton of a humanoid creature with many arms and a distorted cranium with four eye sockets and a giant tail-like appendage coming from the back of it's head appears behind him. That creature had many arms, each arm was doing one shadow puppet of the Ten Shadows Technique. With the help of the black flash, his resolve in truly becoming The Strongest, to not only avenge the Oni Twins, but also help Emilia becoming King of Lugnica, his domain Expansion... Was truly complete
Subaru: Domain Expansion...
As his Barrier-less domain is complete, diverse flowers, shikigamis and creatures start appearing from the ground, some helped Rem, Ram and Emilia to stand up while others started to lash onto the Mabeast, dragging it down in an infinite void of darkness
Subaru: Chimera Shadow Garden
(Best representation i could give with Bing :P)
As it was being dragged down, many divine dogs started bitting on it, making it growl in pain while slowly being sunken into the abyss, being unable to escape from it, goin deeper... Deeper... Until... Everything fades away with an Avalanche of slashes, turning the Mabeast into nothingness
...
..
.
Subaru cancels his domain, making the world turn into it's normal colours, everything was... Clear to him like never before! He had a smile on his face, his deep green eyes shone like never before, it was like everything was clearer, he felt his curse energy flowing like his own blood, his breath, the electric currents from his brain, his brainwaves, it all was... Endearing and so astonishing that he barely could talk, only look towards the trio, and smile brightly, as if he was never a gloomy kid before
Subaru: Yo, Lady Emilia! Rem! Ram! You gals are fine?
???: Amaaazing~ Mister Subaru!
Subaru looked over to the voice, seeing Roswall with an... Forced smile on his face, startled open eyes and sweating profusely
Roswall: I sensed a little trouble on my way back and came in a rush to help out... But seems you're already had it covered... By the way, i like the... New tattoos, they look good on you
Subaru was smiling through nearly all of the clown's speech, till he talked about the... "Tattoos", looking over his body, he saw Sukuna's Marks all around him, gulping a little, he noticed some differences, as if... It was trying to become "his" marks, the pattern was less "pointy" and more... Fluid.
Subaru: it's... A family heirloom, that darkness you probably saw was what ... Awakened the marks... Means that i have broken a new barrier and am ready to continue growing stronger
Roswall gulps as Subaru picks up his sword and puts it back on his shadows, as he was going to walk over the Twins and Emilia, he spoke
Subaru: Now, let's go! I need to lea-
He watches over an dumbfounded Emilia, and slightly Embarrassed Ram and an awe-looking Rem
Rem: Mister... Subaru... You... Helped me?
Subaru: Yeah
Rem: why? I-im dispensabl-
Before she could finish, he appears infront of her and flicks her forehead
Subaru: now listen, you cute maid, you're not dispensable, you're very valuable im the Roswall Mansion, your sister needs you to help her on what she can't do, wich, is, basically everything. Lady Emilia needs her best maid to help her, your Patron needs you as his valuable, caring and strong Maid... And i need a partner who i can rely on...
He remembers Yuji in her, he remember Yuji being fine with dying if it was to save more people and that... Tore him apart
Subaru: Rem... You're not someone who needs to... Hide in the shadow of your sister, you need to be your own person... You're Rem, and... You're unique, indispensable
Rem eyes where starting to fill with tears, as she looks to Subaru and suddenly hugs him
Rem: Lord Subaruuu!
Ram: Barusu...
Ram smiles while looking down, Emilia hugs the both and Roswall sighs in relief.
...
..
.
(Timeskip :p)
After a few hours of the Magic Forest incident, Subaru was in his room, he already finished his homework and finally understood a majority of Lugnica's history and language, he now looks into his reflection on the window, seeing Sukuna in his real Body
Sukuna: It seems our souls are merging more and more, thanks to that pesky witch, she wants you alone, and thinks merging us both with help her out
Subaru: ... What?
Sukuna: Oh, you know, the Witch of Envy, the one you've studied about
Subaru: ... How did your domain killed the Mabeast?
Sukuna: ignoring my call, huh? Well, our souls are overlapping, the Domain is the emanation of the Soul into the real world, guess
Subaru: it means...
Sukuna: soon... You'll be able to use my techniques
Subaru: and soon i can use you, as a Shikigami
Sukuna: so, you want to use me, Brat? Like that Cursed Brat?
Subaru: not without a biding vow
Sukuna: Smart, but what if I don't accept?
Subaru: ... Suffer in silence
Sukuna: (Maniacally Laughing) Sure, Brat! Let's see... Who will suffer in silence!
As Sukuna disappears from his reflection, he goes to the bed, falls down on it and... Sleeps, finally
...
..
.
After waking up, he notices a darn cold affecting the place
Subaru: What the?
His body is trembling with cold
Subaru: the heck?!?
He uses his cursed energy to warm himself up, getting on his feet and walking off his room in pajamas. As he does, he watches Rem outside his room, in a cute winter coat
Rem: Good morning, Subaru! Here, warm cocoa!
She handles him a cup with hot cocoa, not warm, and he drinks calmly
Subaru: what happened
Rem: we have no idea, Subaru! But the whole place is freezing!
Subaru: ... I bet it's Puck
Rem: why?
Subaru remembering how he was almost skewered by ice spikes
Subaru: gut feeling
He smirks, patting Rem's head
Subaru: it's... Nice to see, that you're not gloomy anymore... That's actually suits you much well, Rem.
He smiles at her, and as she gets embarrassed, they walk towards Emilia's room and...
...
..
.
(Credits Rolling)