Saezuru Tori wa Habatakanai: Don't stay gold

Yashiro wants to recruit the violent punk Kuga into the ranks of the yakuza, but Kuga resists every attempt. Things change, however, when he meets Kageyama, the doctor to the yakuza who might just be able to cool Kuga's fiery temper.
(Source: Sentai Filmworks)
Note: Released on DVD with a special edition of the seventh volume of the original manga.