Sanjougattai Transformers Go!

After an incident at Mount Fuji unearths the slumbering Dragotron, Demon Emperor of the Predacons, his minions known as the Four Oni subsequently awaken and seek to restore their unconscious master to full power. To do so, they must obtain five mystical items known as the Legendiscs, which have been hidden away. However, in response to their awakening, two three-member teams of Autobot combiners, each belonging to a subgroup called the Swordbots, have likewise been summoned to counter this new Predacon threat. Answering the call of two human boys, the Swordbot Samurai Team comes to aid Isami Tatewaki, and the Swordbot Shinobi Team teams up with Tobio Fuuma. The two teams use their combination abilities to battle the Predacons, and recruit both Isami and Tobio to help them in their fight. And with the guidance of Optimus Prime, both teams must find all of the remaining Legendiscs—which are located in various points in time throughout history - so as to keep them safe from the Predacons. (Source: TFWiki, edited)

Note: Japan-exclusive sequel to the US cartoon Transformers Prime, commemorating the 30th anniversary of the Transformers series. Released on DVDs bundled with Shogakukan's Terebi-kun (TV-kun) magazine and Kodansha's TV Magazine.