MTL - Eternal Country - Chapter 5 Prepare supplies

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.

This is a story about a legend, of one that can never be forgotten.
Summer, first time down the mountains in 16 years, after being raised by his 3 masters and Fairy sister.

‘Why won’t you follow the Rules of society?’ The rules are the tool made by the strong, so I follow my own rules.

‘Why won’t you just use your brain instead of your brawn?’ Idiot! Have you ever seen anyone use their brain, to get back at an ant that bites them!? No, they just casually step on it.

‘Oh, everyone says you’re a first-class beauty huh?’ well, I’m sorry but even you are not qualified to be my wife. Only a ‘Summer class beauty’ is worthy enough!

‘My enemy is sick?’ Oh, don’t worry, even if you’re on your last breath and I feel it’s beneath me to slap shot you dead. I’ll just fix you up and then beat you!

‘Who am I?’

“I am Summer in the spring, the autumn, and the winter, I’m the world’s first above the heavens!”

Follow me, Summer Day as I step by step become known as the world’s first master, the world’s first doctor, the world’s richest man…… a lot of other world’s number one, but most importantly, The worlds happiest man.

- Description from Novelupdates

I was a genius in the Earthen Plane.