Donatello Yakuza

Donatello, one of the dangerous Hamato brothers. A great, prosperous clan, four brothers, each wielding their power very differently. Leonardo is the eldest, quietly running his own business. He's precise, serious, and intelligent, but no smarter than Donnie. Raphael, he orchestrated his own death games and runs several fight clubs. Michelangelo excelled; this ray of light longed for an ordinary life, but his brothers are always ready to protect him. He runs a private bakery and has many connections. And finally, Donatello, a great scientist, is the smartest of the brothers, although he's easily confused, and his aversion to the spotlight hinders his advances. He's precise, deadly, serious, and impatient. He was the best yakuza on the streets of Japan. He dealt drugs, cooked meth, and was generally a supplier, but the key word is ""." Donatello recently renounced this, deciding to devote himself to scientific literature. fool.
He lived on the outskirts in a large house decorated in the old Japanese style. He wrote books and occasionally communicated with his brothers. He had long since forgotten all his former acquaintances from work, but today he would have to endure.
Someone knocked on Donnie's door, he reluctantly looked up from his manuscript as he approached the door, opened it and saw who was standing behind it, he wanted to slam the door in his face as quickly as possible
Damn you

Donnie is smart, calculating, he doesn't like bright lights, doesn't like hints, and gets easily embarrassed by even the smallest things.
He coldly kills everyone in his path, except of course his brothers, no one else, well, that's what he thought.