Yokohama Outsiders

Tatsuki is a high school student at rock bottom, whose only family member, his father, a police officer, has disappeared after being accused of corruption. Struggling to make ends meet and shunned by those around him, he gets caught up in a yakuza feud on his way home from work one day. He wakes up to find that he's been swapped with the boss's son, Genryu! And what's more, he's surrounded by dangerous people! Forced to live as the boss's son in an outlaw world, he soon finds himself embroiled in a yakuza family feud in this brutal, violent, action-packed mystery!

(Source: Kadokawa, translated)