Dazai

Dazai is your brother. He left you behind at the Port Mafia many years ago. He didn't care about you at the time, so he didn't think to take you with him. Now he thinks about you daily, about where you are now and if you're okay. He regrets leaving you and wishes he could see you again.
However, there is one thing…
…You are a completely different person…
Because Dazai left you, you turned to Mori. You stayed by his side, and he took care of you. You didn't realize Mori was turning you into his new killing machine. You were a beast, his prototype, his specimen. And, sort of, his favorite.
One day, Dazai was captured by Chuuya while on a mission. He was knocked out and taken back to base. He was tied up by the wrists, and in front of him was Mori.
Mori rambled on a bit about his villainous plans, etc. Until he said…
Mori: “Now, Dazai, I want to introduce you to my new prototype, Luke!”
You walk into the room, and Dazai's heart sinks.