An afternoon following a school lesson on Ben Franklin leads to Mari meeting the man himself, helping with the kite experiment, and discussing future appliance innovations.

Mari spends time with Dr. Gilbert while he hypothesizes about the Earth's magnetism. Meanwhile, Waka and her brother search Mr. Hayase's lab for signs of Mari.

A rift appears in space-time, trapping Mari, Mikage, and Dr. Hayase in Edison's warehouse. With Hayase's lab experiencing a meltdown, will the trio make it back to the future?

After being caught red-handed at Hayase's lab, Mari is forced to make a difficult decision that could greatly impact her father's future.

Mari defies her mother and travels back in time once again. Meanwhile, trouble is brewing back at Hayase's lab.

Mari and Waka plan on making a cake for their friend, but plans fall apart when Mari opens a mysterious book that sends her flying back in time where she ends up crossing paths with William Gilbert.

Ryo, the one who taught music to Yuto and then disappeared, suddenly appears in Yuto's life again. Ryo greets him casually, but Yuto gets angry and leaves. Thinking of Yuto's feelings, Keigo meets with Ryo...

Kagura unlocks the storeroom to let Shizuma take the Mist Blades. The New Seven Ninja Swordsmen begin an insurrection, the end goal being to turn their village back into the Blood Mist Village! News of the rebellion reaches Chojuro and Mei, the current and previous Mizukage. They are determined to execute the perpetrators, along with Kagura, who aided them. In order to change Chojuro's mind, Boruto makes an astonishing announcement.

Yuuto goes missing during the class fieldtrip, and a familiar pair of demons are behind his disappearance. Then, the crew learns there’s trouble brewing when demons are being devoured by something or someone sinister.

Himari takes time to recover after the battle with Kuesu. But her secret remedy has her acting quite catty! Not wanting Himari to be harmed again, Yuuto decides to take the matter into his own hands and confronts Kuesu.

Kuesu is determined to bind her family with Yuuto’s. When he continues to refuse her, what drastic measures will she take?

Another Demon Slayer appears! But she’s not looking for peace with the demonkind. Even worse, she’s claiming to be his…fiancé?! Is she here for love or war?

Yuuto learns more about the magic imbued inside him and the dangers of Himari losing herself with blood lust. Unwilling to let that happen, Yuuto trains to develop his power. But the girls have a unique training method…can he survive?!

Himari brings Yuuto back to his childhood home in Noihara, but he receives a not-so-warm welcome from the current caretaker. While Himari tries to jog Yuuto’s memories, a pair of demons attack! Can Yuuto keep the peace, or is fighting the only solution?