Maoyuu Maou Yuusha - Volume 3 Chapter 7, “You Are Not bandits.”

Breasts are NOT supposed to spontaneously grow for no reason.Women's personalities do NOT flip on their heads without warning. These are two things Tsunade believes wholeheartedly.Until Hinata's embarrassingly large girls begin to expand even bigger than before. Heralding her devolution from a sweet and innocent young lady into a foul-mouthed slut with tits like weather balloons. Tsunade intends to find out why.

On a certain day, a certain thought came to Japan’s Sun Goddess. ——Aren’t there too many Japanese people being abducted to other worlds? It’s true that the large majority of Japanese are diligent and docile and soft-hearted, which makes them pretty much the best people to ask for favors. “But recently it’s just gotten way too out of hand…… Oh, I’ve got it! Whenever a Japanese person is summoned, I just have to summon an otherworlder!” And now, every time a Japanese person is summoned, princesses and elves and beastmen and whatnot are reverse-summoned. Under the acknowledgement of the government, they begin living in Japan. Today, too, Japan is at peace. And so begins this laidback isekai cultural exchange story♪

The journey to the martial peak is a lonely, solitary and long one. In the face of adversity, you must survive and remain unyielding. Only then can you break through and continue on your journey to become the strongest. High Heaven Pavilion tests its disciples in the harshest ways to prepare them for this journey. One day the lowly sweeper Kai Yang managed to obtain a black book, setting him on the road to the peak of the martials world.

- Description from novelupdates

A serious accident caused the protagonist’s brain to have an unusual mutation. This changed the brain development that it opened the door to a mysterious universe. Not only he obtained a ‘god-like’ powerful telekinetic control and mental perception, he also had an abnormal analysis and memory capability comparable to super computer. Having such super brain, his rough life began.

Brain development progress 10%…….20%……50%….80%…. …100%

- Description from Novelupdates