This is Transformers run through Japanese folklore until the Hasbro badge stops mattering. Ten short episodes and all of them sprint: Mount Fuji splits open, Dragotron the Demon Emperor of the Predacons stirs in his sleep, and the Four Oni are already out hunting the five Legendiscs before you've finished settling in. The whole pitch is the math in the title, three bodies into one, with two full three-bot Swordbot teams summoned to answer that awakening, which means the combination sequences carry the emotional weight other shows hand to speeches. It never pretends to be prestige television, and that's the charm. It spends its runtime on oni, legends and gattai instead of apologizing for being a toy ad. If you were the kid drawing your own combiners in the margins of a math notebook, this is that impulse animated without a shred of shame.

An incident at Mount Fuji unearths Dragotron, the slumbering Demon Emperor of the Predacons. His servants, the Four Oni, wake up and set out to bring their unconscious master back to full power, which means gathering five mystical items called Legendiscs. The Legendiscs lie hidden at different points in history. To counter the threat, two three-member teams of Autobot combiners from the Swordbots subgroup are summoned by two human boys. The Samurai Team sides with Isami Tatewaki and the Shinobi Team with Tobio Fuuma. The robots use their combining powers against the Predacons and bring both boys into the fight. Guided by Optimus Prime, the teams race to secure the remaining Legendiscs before the Predacons can claim them. The ten-episode action OVA is a Japan-only sequel to Transformers Prime, made for the franchise's 30th anniversary.