Ambiguous Relationship - Chapter 9 - Misfortunes

[ Loki, The God of Mischief, Jest, and Woe, is amused. ][ The Goddess of Fate and Luck is annoyed. ][ You are the cause and center of two gods fighting. ]Ethan Cross, a brilliant doctor in a futuristic Earth, was devastated when he realized that his entire life—and the life of the woman he loved—was nothing more than a source of amusement for a mischievous god.But when another god, the Goddess of Fate and Luck, intervened on his behalf, Ethan found himself at the center of a divine battle, gaining a dangerous but powerful gift.[ You’ve awakened the SSS-RANKED SKILL: Fate Breaker! ][ You’ve awakened a system: The Supreme Fate Breaker System. ]For a fleeting moment, hope returned. Ethan was offered a chance to save Claire, the woman he couldn’t bear to lose.[ You’ve been granted God-Level Authority for three seconds. ][ Do you wish to rewind Claire’s soul trajectory?]“Yes!”But fate had other plans.[ Bug detected. ][ Message included with bug. ][ “It’s from me, your favorite god—Loki, the God of Mischief.” ][ 1-second system override has been taken by the God of Mischief. ][ Your soul has been sent to an alternate universe. ]Now thrust into a world of magic and monsters, where gods toy with mortal lives, Ethan must adapt or perish.

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.

In previous life, I was just a mediocre guy, and accomplished nothing.

After reincarnation, I seize the opportunity of being a legend of the times. In this life, I am the protagonist in Tianxuan World, a great master of martial arts and a founder of making elixirs. What? You want to compete with me in weapon and equipment refining? Then, you should know the Craft God is my disciple…

- Description from Novelupdates

A college student, accidentally reborn into the world of Naruto, becomes a member of Uchiha who is destined to be exterminated.

In this cruel ninja world, in the face of endless wars and exclusion from the village, what will Uchiha Qing do?

PS: Later in the book, the protagonist will develop a system of immortal cultivation. Cultivating Immortals in the Ninja World, have you seen it?

- Description from novelbuddy