Life Simulation: I Caused the Female Sword Immortal to Regret Forever - Chapter 256:

In her previous lifetime, they had married for five years. He meant everything to her, but she was thrown away like an old shoe.

After her rebirth, she gave him a divorce contract preemptively—

“Divorce after one year, the terms of the contract are as follows: husband and wife shall not share a room or bed. Intimacy forbidden?”

He raised his eyebrow.

Who knew that after she got drunk one day, leaning on the headboard, he rested his deep-set eyes on her. “You broke the contract, Mrs, Li.”

- Description from Novelupdates

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.

Suddenly a high school student Subaru Natsuki has been summoned to another world on the way back from the convenience store. With the biggest crisis of his life being summoned to another world and no sign of the one who summoned him things become worse when he is attacked.