The Valatas Chronicles

How should I put it... A princess from a country summoned me to another world. If things follow the usual formula, I must be a hero, tasked with defeating the Demon King. And sure enough... that's exactly how it goes... But for the sake of the beautiful girl, I'll follow the script and play along with the formula... I just never expected that, right at the end of my battle against the Demon King, something would happen...