Two OVA episodes featuring additional stories. Episode 0: Ritsu and Takano used to date back in high school, but broke up due to a misunderstanding. This is that story. Episode 12.5: Hatori and Chiaki go to visit the latter's family. It's really awkward in many, many ways.

Following the horrific assault on the Re-Estize capital city, the Guardians of the Great Tomb of Nazarick return home to their master Ainz Ooal Gown. After months of laying the groundwork, they are finally ready to set their plans of world domination into action. As Ainz's war machine gathers strength, the rest of the world keeps moving. The remote Carne Village, which Ainz once saved from certain doom, continues to prosper despite the many threats on its doorstep. And in the northeastern Baharuth Empire, a certain Bloody Emperor sets his sights on the rising power of Nazarick. Blood is shed, heroes fall, and nations rise. Can anyone, or anything, challenge the supreme power of Ainz Ooal Gown? [Written by MAL Rewrite]

The final hour of the popular virtual reality game Yggdrasil has come. However, Momonga, a powerful wizard and master of the dark guild Ainz Ooal Gown, decides to spend his last few moments in the game as the servers begin to shut down. To his surprise, despite the clock having struck midnight, Momonga is still fully conscious as his character and, moreover, the non-player characters appear to have developed personalities of their own! Confronted with this abnormal situation, Momonga commands his loyal servants to help him investigate and take control of this new world, with the hopes of figuring out what has caused this development and if there may be others in the same predicament. [Written by MAL Rewrite]

With his muscular build and tall stature, Takeo Gouda is not exactly your average high school freshman. However, behind his intimidating appearance hides a heart of gold, and he is considered a hero by the boys for his courage and chivalry. Unfortunately, these traits do not help much with his love life. As if his looks are not enough to scare the opposite sex away, Takeo's cool and handsome best friend and constant companion Makoto Sunakawa easily steals the hearts of the female students—including every girl Takeo has ever liked. When Takeo gallantly saves cute and angelic Rinko Yamato from being molested, he falls in love with her instantly, but suspects that she might be interested in Sunakawa. With his own love for Yamato continuing to bloom, Takeo unselfishly decides to act as her cupid, even as he yearns for his own love story. [Written by MAL Rewrite]