Underdog and Lion

Riku, a university student who was left devastated after his long-term girlfriend was brutally stolen by another man, undergoes a total transformation under the guidance of a charismatic middle-aged man named Yuji! From a "loser dog" to the King of Beasts, Riku aims to become the ultimate lion! Witness the birth of a legendary playboy in the Reiwa era! (Source: Kodansha, translated)