As the Minor Gay Love Rival in Het Novels - Chapter 4.5

Rael screwed up badly. One reckless gamble later, and his guild's entire emergency fund was gone. With debt collectors ready to harvest his organs, his only hope was a single, desperate gacha pull.Ding![Congratulations! Player: Quarterpounder69 has obtained the (Divine) Grade item, Eye of the Beast!][Divine Grade item obtained! All Stats +250][First Divine Grade item obtained! All Stats +100][New title unlocked! [Heavenly Attraction] (Divine)]With no other choice, he consumed the item—only to be thrown into a situation no player had ever faced before.[To ensure fairness, please select a random number. This will determine which boss monster variation you become.]'Uh, I don't fucking know? 69... hmm, maybe not...'[Confirmed.]'Wait—'[Congratulations! You've chosen the Special-Type Boss Monster Variation: The Pay-to-Win Boss.][Congratulations! You've become a Boss Monster!]Armed with broken perks like [Premium Leveling], [Premium Evolution], and [Premium Shop], Rael was thrust into the world of the VRMMORPG game he had been playing.The issue was, he went back in time, specifically, 150 days before the launch of version 1.0.

Xu Yiyang, who was only late in his life when he was middle-aged, returned to 1999 in a dream.

At the turn of the millennium and the turn of the century, he realized a truth:
Not only to be famous early, to start a business and make money, but also early!
………………
New book uploads, new stories, new voyages,
Hope you all support!

- Description from Uukanshu

When The Cute Kunoichis Spied on Their Teacher's Secret is a light novel written by Kazuma Kamachi and illustrated by Ryuushi Tajima.

The story takes place in a world where Japan never ended their isolationist phase, and agents from foreign powers are always threatening to steal the country's advanced technology. In order to combat this threat there has been a resurgence of ninjas that use Strategic Martial Arts, techniques that combine cutting-edge modern technology with a traditional foundation of martial arts and ninjutsu. The story follows Souha Sugiyado, a 17-year old ninja instructor and former ninja prodigy who was forced to retire from active duty by the wounds he suffered in his last mission. Souha's four students are all kunoichi who have all gained the rank of Elite Ninja, the highest official rank available to ninja. However, one day two Shogunate ninja approach him with the news that his four students have gone rogue and have stolen a portable modular nuclear reactor, and thus they ask for his help in bringing his students to justice.

By coincidence, Li Yunmu found a super machine from humanity’s age of darkness. From that point onwards, his ordinary life would never be the same! Aptitude? Innate talent? What are these? Could they be eaten?

I have neither aptitude nor innate skill, but my shadow can level up using hacks. Experience, Ability points, battle prowess… all of them could be hacked. Even while he is asleep or tired, he could still increase his skills.

- Description from Novelupdates