Kuuga:
Driven by the harsh realities of life, Ayasaki Hayate, a youth with 2000 skills, embarks on a completely different path after a single bento delivery. The tragic warrior reappears at the police station, as the ancient war game begins anew. Simultaneously, this youth, amidst despair but never despairing, attracts the gaze of a certain deity.
Agito:
Intrigued by the black warrior, the deity, who had slumbered for eons, once again casts its gaze upon the human world. Yet, its beloved children are tainted with colors abhorrent to the divine, and thus, divine punishment descends. Among the "sinners," a young man named Kamijō Tōma rebels against the deity. [To Aru + ?]
Ryūki:
To resurrect his lost love, a mad fool remakes the world, trapping thirteen Flame-Chasers in an endless cycle of reincarnation, becoming prisoners of fate. (Similar to the world view of the 13 Flame-Chasers' Golden Courtyard, but Kallen's discovery of the Mirror World allows Otto to find an opportunity to control the world). [Honkai Impact 3 PE + ?]
Faiz:
Having concluded a youth unrelated to himself, young Hikigaya Hachiman finds himself adrift regarding the future. What is a dream? In battle against grey monsters that rise from the dead, he seeks to find this answer. [Oregairu + ?]
Blade:
Yuki Yuna Is a Hero.
Hibiki:
Gintama.
Kabuto:
Alien insects descend, changing everything. The Uma Musume can't suppress their desire for speed. The Sun, rising in the east, casts its radiance. The fastest will acquire the authority to change everything... [Uma Musume]
Den-O:
As the lingering dead attempt to erase time, a see-spirits girl encounters souls from different worlds. The train guarding time, where will its destination be? (Book setting: Imagin originally lingered in the sands of time, souls from each world, modified into Imagin, then sent into the past. They have no past memories, they are the lingering dead in time). [Mieruko chan + Re:Zero]
Kiva:
Can a lie become true love? A Fangire princess leaves the answer to this question to her family. Father and son, two generations intersect across time, and together they provide their answers. [Oshi no Ko + ?]
Decade:
The tyranny of the Demon King of Time & Space echoes across all worlds. To acquire the power to oppose him, the Riders entrust their hopes to siblings from an outer world. They embark on their respective journeys, either destroying everything or connecting everything. What exactly do the siblings see in their eyes...? [Genshin Impact + ?]
W:
Yūki Asuna, following her father's footsteps, enters Fūto. Here, she encounters a pair of siblings who call themselves detectives. The wind of Fūto blows the scarf. The two-in-one Rider also watches over Fūto tonight, as always. [No Game No Life + Sword Art Online]
OOO:
Yu-Gi-Oh! Zexal.
Fourze:
Youthful galaxies also have all sorts of troubles. The thoughts of young girls are subtle and unpredictable, but a fool wouldn't care about such things. "Let's be friends!" so says the fool named Yoshii Akihisa, storming into Utahoshi Kengo's life. [Baka to Test to Shoukanjuu + ?]
Wizard:
Hope, nurtured within, is shattered in the Sabbath. The fortunate survivor, Hinata Hajime, becomes a magician. To prevent others from experiencing the Despair he once felt, he resolves to become the ultimate hope, but a second Sabbath is already looming like a shadow. [Danganronpa]
Gaim:
Evolution will not wait for humanity to be ready. Adaptation and destruction, salvation and conquest. Men and women, young and old, enact their royal paths on their own stages, intending to dye the world in their respective colors... [Love Live + ?]
Drive:
The 108 new life forms, meant to benefit humanity, are maliciously tainted by a madman. Kōsaka Kyōsuke, a young detective following in his father's footsteps, is chosen by a strange Belt. The engine has already started, and the authority to press the accelerator is in his hands. [Oreimo + ?]
Ghost:
Fujimaru Ritsuka is killed by a Ghost on her 18th birthday. Under the guidance of an unreliable young man who calls himself Dr. Roman, the girl embarks on her path to gain the approval of great individuals and revive herself... [Fate Grand Order]
Ex-aid:
An unknown Virus begins to wreak havoc. Those who harbor endless dreams of becoming doctors pick up their Gashats. "I will change the patient's fate!" A doctor, and also the strongest player, the story belonging to the doctors begins... [Arknights]
Build:
An evil alien shapes false heroes. To dance in his palm, or to build a new future? The genius physicist Mei must make her choice... [Honkai Impact 3 CE]
Zero-One:
Human malice never ceases. A.I., the mirror of humanity, good and evil. The Humagear Hatsune Miku, endowed with humanity by her creator, will she spread her wings and soar towards her dream, or fall into the trap Ark has prepared for her? [Hatsune Miku + ?]
Saber:
Both a novelist and a Kenshi. As the pages turn, the fate woven by the novelist Itsuka Shiori will intersect with the Seiken. The world here begins its countdown towards its end... At least, that is the fate I saw. [Date A Live]
....
The first story will be Saber, and since it's the beginning, I will retain up to 90% of the original content to serve as a foundational framework for easier writing later. From the second story onwards, there will be more significant changes. However, this doesn't mean Saber will remain entirely unchanged; the characters' personalities will later be made as close to their original counterparts as possible (if feasible). The early stages are for setting the foundation; characters must necessarily make similar choices and experience events corresponding to their original counterparts, otherwise, it would create a sense of disconnect with the broader setting
The plot will encompass both the TV series and movies (depending on their suitability for the storyline). I want them to connect as canon, thus necessitating careful selection. Towards the middle or end, Kamen Riders from other series will make appearances..