MTL - Since 1981 Health School - Chapter 355 made a two-principle error

After dying in an oddly anticlimactic vending machine accident, Kazuki Ren is reincarnated in the demon realm—not as a hero, not as a villain, but as the only human male student enrolled at the mysterious Academy of Ruin, a school where all the professors are demon lords and all the students are powerful, beautiful she-demons.Ren is told he has one task: survive.But there’s a catch. The Academy’s darkest secret is about to awaken, and Ren holds a hidden power that could either destroy the demon world... or rule it.Now surrounded by seductive demons with hidden motives, eldritch tomes, forbidden dungeons, and twisted exams, Ren must master his ability—or be consumed.Magic, mystery, danger, and temptation await in this dark academia harem fantasy.

“Is this man not going to divorce me? Why does he still ask me to warm the bed every night?”

After choking to death on a watermelon, Rong Jiahui thought that she would enter the netherworld and be reincarnated.

But when she opened her eyes, she discovered, to her very horror, that she had returned twelve years into the past…

Looking at the beautiful and awkward “little brother” that would be conferred the title of Marshal in the future for outstanding military service, she almost let out a snort of laughter.

She firmly decided to hug the thigh of this little brother, and climb to the top of her life!

The plan was beautiful, but it had just one problem.

Why had this little brother… suddenly turned into…

A little sister…

- Description from Novelupdates

“You saved me, to repay you, I decided to devote myself to you!”An Ran just did a good deed casually, but was entangled by this black-bellied, ice-cold face.“No... no need, I'm still young,” An Ran sweat madly inside, waving her hands repeatedly.The man, however, was very serious: “I will wait for you to grow up.”But, isn't your image of throwing a tantrum too unbearable to watch?Didn't you say you were like Cold-faced Yama, aloof and abstinent, with an eight-thousand-meter glacial demeanor?A certain brotherhood wiped a bitter tear and said, what's the big deal about throwing a tantrum? Neglecting friends for love, betraying friends for affection, and always have to be ready to be fed dog food. They just want to ask, such a brother, can we return him?