帮我写出关于《小混混们的战争》的内容简介，主要包括电影的主要角色，背景等等，不要过多剧透，结尾可以是开放式的。
A thug in a town named Sang-keun and his gang. When Se-il, whom they fear, comes back to town, they get ready to fight back against him. The film depicts the unpredictable world of males with a compelling storyline and lively images, not to mention outstanding acting of Kim Muyeol.