MTL - Dangerous Survival in the Apocalypse - Chapter 128

Transmigrated into the world of High School DxD, Roy believed he had been handed a life of luxury and glory. Born into the prestigious Lucifuge family, with his Sister Grayfia as his strict yet devoted older sister, he thought he was destined for greatness. 99,997… 99,998… 99,999… 100,000!!But... reality proved harsher: Roy lacked demonic talent and, despite years of training, remained a Low-Class Devil. his peers effortlessly achieve High-Class status, he’s been trapped in a cycle of endless sword practice and ridicule. Yet, he refused to accept mediocrity. Ten thousand sword swings a day, relentless training.. Until one day..[Ding! The Strongest Demon King System has been activated. Access functions to learn more.]---- High School DxD - Main World!1 - High School of the Dead [●] - First2 - Demon Slayer [●] - Second3 - Akame Ga Kill [●] - Third4 - Bladedance of Elementalers [●] - Fourth5 - Campione [●] - Fifth

I met the male lead in prison.

Another entry in what you can call the Proto Harem Series: the books written before the Harem Series that take place in the same world.

It’s about a swordswoman whose student is captured, so she goes to rescue her.