Ghosts Know What I Experienced - Chapter 44.1: He is my wife!!!

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.

Zhong Li, an orphan in the 21st century, was wondering how to collect the fees for his college study on the street, when he was suddenly hit by a car, which threw him into a river. An orphan’s disappearance would not bring too much attention to the world, but this accident gave Zhong Li another chance of living a glorious life in an immortal world. When he woke up, he found himself lying in a magnificent yet strange palace built of all gold, but had no door. An immortal claimed to be his savior and wanted to train Zhong Li with all of his cultivation methods, only because he was too lonely and wanted a disciple to keep him company. When Zhong Li finished his study, the master would tell him how to go out of the palace. Zhong Li never thought that the path to immortality would bring him to the fate of becoming a dragon.

- Description from Novelupdates

First of all, this is not a story where the cannon fodder chambermaid counterattacks and gives the main wife a beat-down! As a lowly s*ave who had been sold a total of six times, Xiao Hua has long become apathetic to her situation. In her past life, she was a cannon fodder chambermaid who was beaten to death. In this life, she decided to turn over a new leaf and live honestly, yet in the end still ended up being sold off. This prince’s estate seems to have pretty good benefits? She could be released at twenty-five, and they’d arrange a place for her to live under their jurisdiction? They’d even get rid of her s*ave records? Great! That’s great! Xiao Hua thus decided to stay in the Jing Prince Estate and do her job properly. It’s a shame she could never overcome the whims of fate…. The master she serves is a “mute boy”, with several influences above him watching like tigers eyeing their prey. To say she doesn’t want to be pampered is definitely a lie. This is the road to survival of a “discreet girl” who clings on to her master’s leg and is solely pampered, yet feels that he never pampers her. The road from a cannon fodder chambermaid to a beloved imperial consort is a little long….

...[Inside an underground basement]“You are going to die for nothing, hahahaha,” the old man's voice thundered through the room, sending chills down my spine.Step.With a swift and ruthless motion, he lunged forward, his sword slicing through the air and slashing my throat, crimson droplets staining the darkness.“We'll see,” I whispered defiantly, my final words escaping as a mere breath against the impending darkness.Slowly, inexorably, my consciousness slipped away, and I descended into a deep, unfathomable slumber.“Huh!?” My eyes fluttered open, and I found myself seated in a bustling tavern, the air thick with laughter and the clinking of glasses.In front of me stood a captivating lady, her beauty juxtaposed with an angry furrow upon her brow, threatening to shatter the harmony of the jovial scene.“Don't follow me around!” Her words pierced the air like shards of ice, the intensity of her emotions palpable as she cast a resentful glare in my direction, before swiftly departing from the tavern....Am I trapped within the confines of a game? The fragments of my shattered common sense scattered before me, leaving me to question the very fabric of my reality.