Bungo Stray Dogs: Pinky Promise

I'm terrible at writing blurbs:

As a "failed specimen" created at a military ability research base, he escaped destruction by awakening his ability in time and developing a powerful physical talent. Fukuzawa Yukichi found him in the Slums.

Fukuzawa Fumiyuki's life before age seven [not his actual age] was miserable, but after turning seven, surrounded by kindness and warmth, he could finally become a real human, like Pinocchio meeting the Blue Fairy.

He's a genetically engineered human based on Nakahara Chuuya, not Nakahara Chuuya himself. He has his own unique experiences and soul.

Ranpo [clinging to Fumiyuki with all four limbs]: "Fumiyuki is mine, he's mine! All you other monsters and demons, back off!"

Nakahara Chuuya: "Well, I mean... no matter how you look at it, he should be my little brother, right?"

Verlaine: "One little brother, two little brothers, two, two, two..."

Dazai Osamu: "Ah, two slugs together really are even more disgusting and clingy."

Boss Dazai: "Indeed. Black Sludge upstairs, please keep your partner in check and stop him from barging into someone else's home to bother their child."

Nakahara Chuuya: "I'm not bothering him! Ugh, why are there two mackerels in this world?"

Dazai Osamu: "Look what I've found. A stinky lump of something-or-other is talking!"

... [I've run out of ideas for what comes next.]

Appearance: light orange hair, pale blue eyes like a lake. Trained in Fukuzawa Yukichi's assassination techniques, with a self-healing physique, top-tier combat talent, and the strongest physical fighting ability around.

Gentle, polite, considerate, and attentive. Deep down, stubborn, forceful, and an instinctive dog person.

An all-around domestic angel who earns money to support the family outside and takes care of his father and his much older "little brother" at home.

Ability: Pinky Promise. [A support ability that can evolve later.]

Theme: I want to give Yokohama one more angel