On a bright, peaceful day, siblings Nunnally and Lelouch Lamperouge take a moment to relax under a tree. When Nunnally asks him to tell her a story, Lelouch, who is unflinchingly resolute in doing his utmost for his sister, makes unique use of his Geass ability, breaking barriers to tell the most entertaining story he can. Awakening alone under the tree, the previously blind Nunnally finds that she can see again and immediately spots a strange rabbit that resembles Anya Alstreim, the Knight of Six. The sight of this rabbit sends Nunnally falling down a hole, leading her to a colorful wonderland. Narrated by Lelouch himself, Code Geass: Hangyaku no Lelouch - Nunnally in Wonderland follows the lost Nunnally as she searches for a way back home, meeting a slew of colorful, familiar characters along the way.

In the vast world, planes converge and numerous races thrive. A gathering of extraordinary talents unfolds, where one after another, supreme beings from the lower planes come forth. In this boundless realm, they weave captivating legends that inspire admiration, pursuing the path to dominance.

Deemed a "good-for-nothing" for his low level and lack of a god-given Gift, Allen is stripped of his noble status and banished from the Duchy of Westfeldt. But Allen has a secret: he was a great hero in a previous life, and he's thrilled for the chance to finally live the way he pleases! His drama-free existence, however, is soon interrupted by a desperate encounter with his ex-fiancée. As a former hero who still possesses the incredible powers from his past life, Allen can't ignore someone in need—no matter how much he might like to! And so begins the new heroic saga our former hero never wanted!