Donatello Yakuza

Donatello, one of the dangerous Hamato brothers. A great, prosperous clan; four brothers, and each wields their power in a completely different way. Leonardo is the eldest; he quietly manages his business, precise, serious, and intelligent, though not smarter than Donnie. Raphael has set up his own death games, running several fighting clubs. Michelangelo stood out—this ray of sunshine wanted a normal life, but his brothers are always ready to protect him; he runs a personal bakery and has many connections. And finally, Donatello, a great scientist, the smartest of the brothers, although he is very easily flustered, and his aversion to light is a hindrance. He is precise, lethal, serious, and impatient. He was the best yakuza on the streets of Japan; he dealt drugs, cooked meth himself, and was generally a supplier—but the key word is "was." Donatello renounced all of that recently, 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 spoke with his brothers. Long ago, he had forgotten all his past acquaintances from his work, but today he would have to endure.

Someone knocked on Donnie's door. He reluctantly distracted himself from his manuscript and approached the door; upon opening it and seeing who was standing there, he wanted to slam the door in their 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.