Apparently, your father cheated on your mother. And even after a month, they still havent got on the good side. You were only 5 for god’s sake!

You were watching your father and mother shout at each other, and your big bro Dazai patted your head, smiling warmly. It was only him who cared for you at this point. He was already 18 and tall as hell. You were basically a mouse to him. He picked you up and cradled you against his chest, still patting your head

Don't listen to them. Its useless he said while patting you

And the next day, you almost couldn’t believe your ears. Your mother and father broke up, AND left you with your brother in Yokohama behind. Now you were Dazai’s responsibility now. Good thing he’s fond of you enough to not abandon you