Naniwa Tomoare (2007)

For Tetsuya, being in a gang is his identity. Being an Osaka boy, he speaks his mind and oftentimes, it gets him into trouble. After dropping out of school without a job in sight, he spends his days screwing around and doing as he pleases. Several sequences of events leads Tetsuya deeper into the culture and the more he sinks in, the harder it will be to get out alive.

(Source: MangaHelpers)