MTL - After the Divorce, the Boss Dressed As My Dog - Chapter 81

Frank, a mercenary known for his cold ruthlessness, decides it’s time to leave the bloody world of the underworld behind. But the underworld has no plans of letting him go. Relentless enemies from his violent past keep hunting him, and eventually, they succeed—Frank is killed.But fate has other plans. Instead of staying dead, he is mysteriously reincarnated into the body of a cop in a world filled with crime, corruption, and dark secrets. With the help of a strange, all-knowing system, Frank is given the chance to live again—this time, to prevent crime before it happens.

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.

A chance to change, to challenge destiny, making dreams a reality, and live a legend! A regular man gains a system that allows him to turn into a fish!

- Description from Novelupdates

The tale of Oliver.
An orphan boy from a Mine, in 19th century Europe, filled with Magic.