Dying is usually a one-way trip, but for the man now known as **Ryuuji Tsurumi**, it was just a very violent transmigration to a new job.
When he first opened his eyes in this unfamiliar bedroom, the disorientation felt like a physical weight. Then came the flood. It wasn't just memories; it was a complete data dump of a life he hadn't lived. He was no longer a guy from the "real world." He was a graduate of middle school living in Chiba, currently killing time before his first day at **Sobu High** on April 8th. More importantly, he realized he had a younger sister—**Rumi Tsurumi**.
If the name sounded familiar, it was because Ryuuji was a fan of *Oregairu* in his past life. Rumi was the lonely, cynical elementary schooler that Hachiman and Yukino tried to "save" during that summer camp arc.
But as Ryuuji sat up at 9:00 PM after a long, dizzying nap, he realized the "plot" was much, much messier than a single rom-com light novel.
Ryuuji spent the next hour scouring the internet on his phone, his jaw dropping lower with every search result. This wasn't just Chiba; this was a logistical nightmare of a crossover.
The global economy was a battlefield of titans. The **Shinomiya Zaibatsu** sat at the top, rivaled only by the **Suzuki Zaibatsu**, the ruthless **Momobami Clan**, and the prestigious **Arima Zaibatsu**. Education was even weirder. In the news, he saw advertisements for **Shuchiin Academy**, the elite **Advanced Nurturing High School** (where the government supposedly groomed the elite), and the bizarre, high-stakes **Hyakkaou Private Academy** where goes most crazy and reckless heirs of high class families.
"Wait," he muttered, scrolling past a gourmet food blog. "**Totsuki Culinary Academy** and **Dark Cooking Society**, **The Gourmet cells**? **Fujimi Academy**? This isn't a world; it's a mosh pit."
He saw a promotional ad for the **Sirzechs Hotel** in Kyoto—a name that sent a chill down his spine. And after searching in google maps in the surrounding of Tokyo, Ryuuji not only find the existence of just **Kuoh Town**, he also found **Tokonosu city** and **Fuyuki City**. If those places existed, then "normal life" was a thin veil over a world of devils, zombie apocalypse and holy grail wars.
"I'm going to need more than just a high school diploma to survive this," Ryuuji whispered.
Right on cue, a translucent screen flickered in his vision. The **Diary System** had initialized. It was a classic "Cheat" from the isekai stories he used to read: write down spoilers about the future, send them to the "heroines" of this world, and get rewarded based on the impact and length of the entries.
The catch? Every entry had to be at least **1,000 words**.
Ryuuji didn't want to start with the girls he'd eventually meet at Sobu High. As much as he loved to talk about his previous life favorite **waifus**, they weren't in immediate danger. Their "stories" were still a year away from hitting their peak.
No, he had started with the most tragic figure in recent memory: **Ai Hoshino**.
He spent the next half-an-hour pouring his heart into the leather-bound book. He wrote as "Nanashi," a nameless observer. He laid it all out—the secret pregnancy, the identity of the father, the stalker Ryosuke, and the exact moment the knife would find its mark. He even gave her a lifeline, pointing her toward a certain "Sleeping Kogoro" and a pint-sized genius in Beika Town.
He wrote about the nature of this world, the overlapping "plots," and warned her that her life wasn't a script unless she allowed it to be. By the time he closed the diary, his hand was cramped, but he felt a strange sense of satisfaction.
The diary glowed.
**[System Message: Entry Complete.]**
**[Word Count: 1,142 words.]**
**[Evaluation: High. You chose to save a life over personal indulgence. Calculating rewards...]**
Ryuuji held his breath. The rewards in these systems could be anything. He could get something world-shattering like Gilgamesh's *Gate of Babylon*, or something uselessly specific like *Yukinoshita Haruno's used stockings*.
Fortunately, the system was feeling generous.
**[Reward 1: Golden Rule (Rank A - Passive)]**
*Description: The fate of being fated to a life filled with riches. You will never have trouble with money, no matter how much you spend or how little you work.*
Ryuuji exhaled a breath he didn't know he was holding. As a student living on a meager allowance while his parents were away on business, this was the ultimate quality-of-life upgrade. No more counting yen for convenience store bentos.
**[Bonus Reward: Hamon (Ripple) Breathing - JoJo's Bizarre Adventure]**
*Description: A martial art centered around controlled breathing to produce energy identical to the sun's rays. Enhances physical strength, heals wounds, and slows aging.*
The system noted that this bonus was granted specifically because he focused on "people in need" (Ai) rather than just his "waifus."
Suddenly, the wind picked up outside his window. Two crisp, high-denomination bills—10,000 Yen notes featuring Shibusawa Eiichi—fluttered through the open window, dancing in the air before landing perfectly on his desk.
Ryuuji stared at the money.
"Okay... so the Golden Rule doesn't waste any time."
He sat cross-legged on his bed and attempted the first breathing pattern of **Hamon**.
*Sssssss-haaaaa.*
A jolt of electricity-like warmth surged through his diaphragm, spreading to his fingertips. It felt like drinking a liter of espresso without the jitters. His vision sharpened, the slight lingering dizziness from his transmigration vanished, and his muscles felt oddly firm.
He thought about the implications. Hamon wasn't just a weapon against vampires (though in a world with Kuoh, Tokonosu and Fuyuki, that was a huge plus). It wasn't just a health booster. It could heal injuries and optimize the body. And give you enough power to repel low rank stray devils or low rank curses.
"Rumi could use this," he thought, thinking of his new little sister. She was small and frail-looking; Hamon would give her the physical confidence she lacked.
Then, his mind wandered to the other girls who would eventually receive his diary. **Kaguya Shinomiya**, for instance. The poor girl was brilliant, but she was often teased by the fandom for her... lack of "assets."
"If Hamon can stimulate cell growth and blood flow," Ryuuji smirked to himself, "I might be able to save more than just lives. I could save some pride. Nobody's going to call Kaguya an 'airport' if I can help it."
Ryuuji tucked the 20,000 yen into the table and looked at the diary resting on his nightstand.
He had successfully written the darkest timeline of *Oshi no Ko*.
But tomorrow was another day. He still had a "sister" to look after, and in a few days, he'd be stepping into **Sobu High**. He'd have to deal with the "Winter Flower" Yukinoshita, the "Nice Girl" Yui Yuigahama, and the cynical Hachiman Hikigaya—though with Ryuuji in the mix, Hachiman's "loner" philosophy was going to take a serious beating.
He lay back on the bed and thought, "This world is a mess," Ryuuji muttered as his eyes drifted shut. "But at least I've got a cheat."