
Sadly, criminal law in Japan does not recognize self-defense in the Western style. Basically it amounts to the injuries sustained on either side, rather than the reasons for the fight or assault. In this case, the mother suffered the worst injuries, so the younger brother would likely be charged as a full-blown criminal. Japanese self-defense mostly relies on the victim either running away, or calling the police before fighting back, even then it is ambiguous. For most Westerners, this is tantamount to letting any aggressor win the fight or fire the knockout blow before the victim can react. The victim cannot prove that any physical retaliation was in genuine self-defense unless there was a witness (unlikely).
It is humiliating and short-sighted, narrow justice, but this is how it works in Japan.

I was angry in the first chapter because the younger brother does what he wants, and gets angry when his older brother is a piece of shit to him. Yeah sure, it is right for him to feel angry from the neglect, but who is the one taking care of the younger brother and the house when the mother is basically not there? Yeah, older brother selling his body for money so that they can live not on the streets and starving. AND BEING SO ASHAMED ABOUT IT AS TO NEVER WANT TO TAINT THE YOUNGER BROTHER.
I don't see the younger brother taking the initiative and getting a job and helping out so that the older brother doesn't have to prostitute. And the younger brother KNOWS they are poor. He never had any ground to judge because of his failure to act.
And now younger brother goes and humiliates the older brother AGAIN. Like the older brother must have already been ashamed from the 1st chapter IN PUBLIC, and how this humiliation extends to the home?
I want to keep reading since I like this story, but lil' bro better freakin shape up before deciding he wants older bro for himself forever.#-.-)

This mother knows that Law is in love with Jesse. Isn't that alone a major reason as to why LAW DOESN'T WANT TO LEAVE THE COUNTRY?
Like holy crap, lady. You may be rich and know the path to wealth, but obviously you care more about that then the feelings of your son being dragged along because of it. From what I see, Law has been carrying out what you asked of him excellently, and then some. It's not impossible for a friendship or love to result. Don't demean the things that you don't understand without experiencing it first-hand. You need to know the extent of Law's and Jesse's love in order to know what your son was getting at when he was using every convoluted and ridiculous arguement in order to stay behind.
Dear Amano, please recall the words "self-respect". It is clear that the object of your affections is not interested, acting all nice towards you while refusing to accept your feelings. Quite plainly, he is being unfair by leading you on with his actions. Please understand and move on. The other party doesn't know and much less recognize what he will have lost.