Betrayed, I Met The Demon Lord Novel

Van and his companion Magus are reincarnated into a magical world with a mission: defeat the demon lord. While Magus receives powerful, advantageous abilities that attract a harem of followers, Van struggles with difficult skills that make his existence miserable. Despite the hardship, Van perseveres through sheer determination. Their quest culminates in victory over the demon lord. However, Van's triumph turns bitter when he discovers that his girlfriend from this new world has become part of Magus's harem, taken from him by his supposed friend. Devastated by this betrayal and loss, Van makes an unexpected decision. Rather than confronting Magus, he seeks out the defeated demon lord with an shocking proposal of his own. This unlikely turn of events sets Van on an unforeseen path, as he approaches the very enemy they were sent to destroy.