MTL - It’s a Stepmother, Not a Sister [70s] - Chapter 133 Fat

Xin Yun, a sarcastic young man, traveled to an unknown world by chance, but lost his chance to become the strongest because of his obsession with women... or sex. In a collision of the powers of nine powerful men, an incredible thing happened. Xin Yun was reborn back to the time when he traveled to the Isekai world. A fantasy journey is about to begin... [The comic adapted from this novel is popular all over the world]

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.

This is actually the story of a teenager who, after the devastating and spartan-like training of his crazy cool/Gong teammate, turned into a super amazing point guard that could blow up the skies even though he may seem low-key on the surface.

Also, Nie Chuan is Reese’s first love.

Nie Chuan: I’ve decided to promote you to becoming my best friend!

Reese: If I can be your best friend, it just means that you have no friends.

Nie Chuan: Hey! How could you say that! Do you know what it means to be my best friend?!

Reese: I’m sleeping.

Nie Chuan: It means that when I get married, my bride may not necessarily be her, but my groomsman must be…

Reese: The groom must be me.

Nie Chuan: What– you want to snatch my bride away?! You’re too inhumane!

Reese: Sleep.

- Description from Novelupdates

His friend and his wife betrayed him. The only thing left to him was his massive debt and his precious daughter. He was without hope as he lived at the bottom. However, a last chance had come to Sungyoon. He was a ‘man without a heartbeat’, and he will explore the Moon’s Labyrinth. He’ll explore the parts of the dungeon yet to be seen!