Saezuru Tori wa Habatakanai: Don't Stay Gold

Eishin Kuga, nicknamed "Mad Dog" due to his aggressive behavior, is a young hothead who gets into a fight with his underlings in front of Yashiro, his longtime friend. Yashiro wants Kuga to join his yakuza group, and to facilitate this, Kanji Kageyama, an underground doctor, allows Kuga to temporarily stay with him. Kageyama is tasked with convincing Kuga to join Yashiro's organization, but he's initially unsuccessful due to Kuga's aversion towards Yashiro.