one sword to rule them all

[Mature Content] [NO NTR] The day dungeons appeared on Earth, everything changed! From ordinary beasts to monstrous ones, attacks were common throughout the globe, and no one was safe. After countless studies using these beasts as subjects, Humankind developed a serum capable of awakening incredible abilities in humans, leveling the battlefield. With the serum came heroes and villains, those who wished to use their powers for good or bad. The Garmony Upper School was a place for the elite with the sole purpose of creating heroes to fight the villains and explore more of the dungeons after the beast attacks increased for no apparent reason. Damian Romero, a youth who received the serum after turning 18, yet got no unique ability. It was not uncommon for one to not receive power, but it was still a blow to one's pride. He went rogue after the news, drinking alcohol and having a good time with women, and it was at that moment, when he was putting his toy to play, he got a surprise. [All-in-One System Unlocked] Damian's unique ability was a system with multiple functionalities, but after he studied it, it seemed this system worked with a different type of coin called Erotic Coins! Improve his body? Buy any item or unique ability from his system's store? All Damian needed was Erotic Coins, and he knew how to earn them! ~~~~~ The MC will not start as a villain, but something will shift his mind in the future.