Light Novel Volume 20/Synopsis

Prologue: Believing Sloth Will Save the World
After receiving a hint from S'yne's Sister that the organization behind the waves might attack Raphtalia's World soon, Naofumi and his party prepare to head back to their world. As they wait for the next wave, they say their goodbyes and discuss with Lyno the information they know about the enemy. Shildina gets permission from her Legendary Ofuda to travel back to her home world and L'Arc is strangely adamant about coming along.

Chapter One: Prisoner Transport
As the wave between Glass' World and Raphtalia's World opens up, Naofumi and his group head back to their world. They also bring along the captured Mald who had been tortured to reveal information about the enemy party. When they walk through the portal, the Legendary Weapons become unsuppressed and Naofumi is able to use his Shield again. They find Trash and update each other on the latest events. As they talk, Naofumi learns that Ren attempted to help the village in his stead, however the Sword Hero collapsed after being overwhelmed.

Chapter Two: Training for an Obstinate Man
Naofumi and Trash continues their discussion on the enemy back at the Melromarc castle. With Naofumi's connections and past history, Trash asks him to negotiate with the accessory dealer Hickwaal in order to reverse-engineer the otherworldly accessories. After the talks were complete, Naofumi teleports to Zeltoble with Raphtalia, L'Arc and Therese to talk with the accessory dealer. They meet the accessory dealer and after some initial pleasantries, Naofumi commissions him to analyze the otherworldly accessories Lyno was able to steal from the organization behind the waves.

However, once Naofumi was almost finished his business, L'Arc burst into the conversation - pleading for the accessory dealer to train him in accessory making. At first, the accessory dealer says no, however L'Arc's obsessive and passionate begging finally convinces the merchant to bring him in as an apprentice. It seems that Therese's obsession with Naofumi's accessories had made him jealous and he believed that becoming a master craftsman was his only way to "keep" Therese. Naofumi and Therese know that L'Arc is delusional but allow him to start his training anyway.

Chapter Three: The Sword Hero's Sense of Responsibility
Finally, after the negotiating was complete, Naofumi and Raphtalia returned to the village where they are welcomed back by the whole village. He is happy to see that the village is doing well and that the villagers have even leveled-up since he was last there. After dealing with the exhausted Ren and rampant Gaelion and the newly classed-up Ruft, Naofumi asks Filo to get in contact with Fitoria. He provides all the information he knows about the vanguards of the waves and the library rabbits (who play a similar role to the filolials). Fitoria then invites Naofumi to the filolial sanctuary.

Chapter Four: The Filolial Ruins
The next day Naofumi and the other Legendary Heroes arrive at the filolial sanctuary. Investigating and cleaning up Fitoria's cluttered nest, they find various powerful weapons among the junk which they are able to copy. Among the various weapons, Motoyasu finds the Dragon Clock Hand (or Minute Hand of the Dragon) spear and sticks it into a receptacle for it. The spear is imbued with an incredible, but unknown powers as he does so. However, this has no effect on the other weapons.

As the group continue to explore the ruins, they end up in a stone chamber similar to the curator's base in the Ancient Labyrinth Library. Just like what they found in Glass' World, they find their own vial of the red poison and inscriptions on the wall cryptically noting the true nature behind the waves. The heroes unlock their 0 series weapons from the poison and ponder the history of the waves.

Chapter Five: Village Abnormality
Returning to his village, Naofumi is greeted my Melty. She is apparently overwhelmed by her new responsibility. However, before they can finish their discussion, Naofumi receives an emergency warning from S'yne's Sister. Before he can react, the village in engulfed in a powerful magical energy and the villagers panick. When the dust settles and Naofumi regains his bearings, they are surprised to find that the village has been transported to some unknown location.

Chapter Six: Encounter with Extinct Monsters
Realizing that they have no idea where they are, Naofumi checks in with everyone and organizes several scouting parties to investigate the nearby area. As Naofumi explores with his own party, they find unusual balloon monsters which have apparently been extinct for many years. They also find that the nearby region looks very similar to their Siltvelt but they head back after the designated time.

After a quick discussion with the excited Rat, Naofumi learns that Ren and his party haven't returned yet. Fearing trouble, he, Raphtalia, S'yne, and Chick follow his path. Bizarrely enough, it seems that some of Naofumi's power-up methods are no longer functional.

Chapter Seven: Double the Shield Heroes
As Naofumi and his group run to find Ren's party, they find him fighting against two powerful enemies. Apparently, these two enemies attacked Ren and his group as soon as they saw that he was wielding the Legendary Sword and they ignored Ren's attempts at diplomacy. Strangely enough, the enemy wielding the shield had similar abilities to Naofumi while the one wielding the scissors had similar abilities to S'yne. However, the fight was stopped once Melty's Shadow held one of the enemy's companions hostage.

Using this hostage, the enemy is forced to engage in diplomacy. The one wielding the shield is called Mamoru while the one wielding the scissors is named R'yne. After realizing that Naofumi and his companions are friendly, they stop being hostile and the hostage is released. During the talks, Naofumi realizes that they have been sent back into the past when there were only 2 legendary heroes. Raphtalia also recognizes Mamoru as a legendary Shield Hero of the past.

Chapter Eight: Hero Worship
Shocked that each other are both Legendary Heroes, Naofumi and Mamoru confirm that they were both summoned from modern-day Japan. After exchanging some quick information, Naofumi leads Mamoru and his party back to the transported Lurolona Village. After official introductions, the two group talk and eventually are able to get Mamoru's reluctant trust. After assigning Rat to research the cause of their journey back in time, Mamoru and R'yne lead Naofumi and his party to their city.

Chapter Nine: Ancient Siltran
Information to be added later on.

Chapter Ten: The Evil Researcher
Information to be added later on.

Chapter Eleven: Bread Trees and Bread Troubles
Information to be added later on.

Chapter Twelve: A Determination to War
Information to be added later on.

Chapter Thirteen: Online Trolling
Information to be added later on.

Epilogue: Different Constellations
Information to be added later on.