Please Be Patient, Grand Duke - Chapter 5.1

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.

He was once a great Immortal, but his attempt to ascend the Nine Heavens ended in failure. Reincarnated on the Blue Star, as he opened his eyes, he found himself with an adorable daughter. And a stunningly beautiful wife?“Daddy, can you cast a spell for me?”“I could even pluck the stars from the sky for you.”

There is luster in the east, and it is named Dahuang. “
In the rumors, ignorance, poverty, backwardness, and wildness. “
– bullshit. “
Queen of the Great Desolation, cold as frost. “
Supported by the national teacher, and the golden boy and jade girl of the national teacher, they are deeply in love, a stunning couple, and unparalleled. “
– bullshit. “
The queen died suddenly, and the national teacher mourned. According to the instructions of heaven, they traveled thousands of miles and finally found their reincarnated lover. From then on, the prince and princess lived happily in the castle…
——Crap! “

- Description from novelbuddy

“Young man… if you could go back in time, what period would you like to be in?”