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
Arriving in the ancient nation of Siltran, Naofumi discovers that it is the predecessor of the nation of Siltvelt. However, due to attacks from the waves and the nation of Piensa, Siltran is in partial ruin. Apparently, Lurolona Village had transported to the middle of a hostile zone between the two nations. While debriefing, the heroes are able to learn that S'yne and R'yne originate from the same world and that unlike Naofumi, Mamoru can attack and damage others despite being a Shield Hero. Learning that both sets of heroes are trying to fight the save enemy (the self-proclaimed god), R'yne offers to teach S'yne a transformation technique from their people while Mamoru gives Naofumi a prototype shield to copy.

Chapter Ten: The Evil Researcher
After concluding his discussion with Mamoru and registering at the dragon hourglass, Naofumi returns to his village. As he arrives, he is greeted by the Vassal Whip hero Holn who has been "terrorizing" his village with her overzealous investigation of its residents. It is revealed that Holn is Rat's ancestor and is an even more accomplished, albeit reckless, alchemist. After a brief discussion, Holn agrees to research the village's displacement in time and hopefully find a way back. Afterwards, Naofumi is convinced by Melty to improve information gathering and finances by restarting trading operations.

Chapter Eleven: Bread Trees and Bread Troubles
The next day, Naofumi wakes up to find the village in a commotion. It turns out that in less than a day, Holn was able to develop a plant that produces bread-like fruit. Afterwards, he was went the village kids to Mamoru to receive permission to start trading. With Siltran low on supplies, Mamoru was happy to receive the extra help. While this was occurring, the children from Naofumi's village started making friends with the children under Mamoru's care. Naofumi then suggests bringing some of Mamoru's children like Cian along to teach them how to trade. Mamoru accepts and also decides to come along. Trading efforts start off very well.

Chapter Twelve: A Determination to War
Unfortunately, soon after the trading had begun, Piensa had starting marching towards Siltran to take it over. It is clear that on even ground, Piensa could easily destroy Siltran with their dragon army. However, despite this, Naofumi and the villagers of Lurolona Village decide to stand with Siltran and protect their village. Wyndia also gave Ren permission to revoke his vow to her that he would not kill any dragon. After drafting a plan to confront the Piensa forces, Naofumi's team prepares for war.

Chapter Thirteen: Online Trolling
As the conflict began, Ren led a large team to confront the dragon battalion - hiding the fact that he is a Legendary Hero. After the battlefield was setup and Piensa's forces were where Naofumi's team wanted them, Naofumi finally charged into the field. Behind him was a massive stamplede of wild animals he had collected using his Hate Reaction skill. Ren cast Liberation-class buff magic on the wild hoarde as they charged towards Piensa's forces. Naofumi's team was able to escape as the buffed wildlife was able to overwhelm Piensa's forces. As the bulk of Piensa's forces fell into disarray, Naofumi found the traitor who kill Siltran's king. He and Ruft capture the traitor. Eventually it became clear that Piensa was losing and the attacking forces started to flee. It seems that all aspects of battle ended in victory.

Epilogue: Different Constellations
In celebration of their victory, Lurolona Village puts on a feast as people start to bond. Rat and Holn discuss their interest in research while Eclair asks Ren to help her become a better leader. Finally, Naofumi, Melty and Raphtalia look at the stars, promising that they'll get back to those they left behind.