OVAs of History's Strongest Disciple Kenichi bundled with volumes 46, 47, 49, 53, 54, 55, & 56 of the manga.

The half-divine King of Uruk, Gilgamesh, was considered but a paltry legend... until his majestic tomb was discovered in the Middle East. This imperial crypt drew scientists from across the globe to the land, and with that came recognition of their fame. In a joint effort, they built Heaven's Gate in pursuit of advancing human knowledge. One day, a group of terrorists driven by greed attack Heaven's Gate, causing an explosion within the facility for archaeological excavation. The resulting phenomenon had much more impact than anyone could have imagined. More specifically, it triggered the birth of supernatural beings. In the midst of this mess, two siblings by the names of Kiyoko and Tatsuya encounter mysterious men with supernatural powers who, despite the scientific crisis around them, claim the ability to restore good to the world. Nevertheless, these seemingly heroic and all-powerful creatures act under the rule of factions. Are they here to save the world, or destroy it?

Ryousuke Hazuki is a young man whose heart has been stolen away, stopping by the local floral shop daily in order to catch a glimpse of the beautiful Rokka Shimao, the shop's owner. In hopes of getting close to her, he decides to get a part-time job at the shop, but before he is able to make his move, he runs into a major roadblock: in her apartment dwells a ghost who claims to be Rokka's deceased husband. Atsushi Shimao has quietly watched over his widowed wife ever since he passed three years ago. However, Hazuki is the first person to ever notice him, and the two quickly find themselves at odds: the jealous Shimao attempts to thwart the suitor's advances and possess his body, while Hazuki simply wants the ghost to pass on for good, allowing Rokka to move on from the past and him to be with the one he loves. As both men refuse to let go of their desires, an unusual relationship forms between a troubled woman, an unrelenting ghost, and a stubborn man in love. [Written by MAL Rewrite]

After the final downfall of the rogue Bakugan Naga, peace was brought back to Vestroia. With the help of Danma Kuusou, his companion Pyrus Dragonoid, and other Battle Brawlers, the Infinity and Silent Cores were combined and the realm was recreated. However, New Vestroia will not be given any respite as humanoid alien invaders, the Vestals, arrive and conquer the Bakugan world in one fell swoop. Armed with a fearsome machine capable of restricting Bakugan into their ball forms, they aim to enslave the race as a form of entertainment. Now, the only force standing in their way is the Bakugan Battle Brawlers Resistance—a group of humans, Bakugan, and Vestals who oppose the idea of annihilating a sentient race. Led by Danma, they must venture into enemy-occupied New Vestroia and repel the invaders, to assure the survival of the entire world. [Written by MAL Rewrite]