After Spider Island incident Peter's life gets turned upside down after he saves a woman's life who turns out to be more than what she appears to be leading to his love life to take a strange turn.

Rias after trying everything to end her engagement decides to get help from a different world. After getting some forbidden documents, she finds a spell to summon heroes from another world. After convincing Sona to help with the magic something happened and instead of summoning a hero they were sent to their world.