the story is similar in the way how how both boys have a sense of violence and unawareness to social construct yet they both show signs of wanting to redeem themself because of their own consequences in the ending.
Both movies deal with characters who become fugitive after domestic violence-related incidents. The age of characters are different though, in Himizu the leads were teenagers while in Soiree they are early adults.
Both are about aimless boys and their awful life; their families are broken, they have anyone to trust. They end up meeting girls to be by their sides. In both movies there is some yakuza. In both they commit a crime.