The series picks up immediately after the end of the third season, six years after the battle against Unicron. The master computer at the heart of Cybertron, Vector Sigma, becomes unstable, threatening to destroy the planet. Meanwhile, a new group of Decepticons, the Headmasters, shows up to cause trouble for the Autobots. The new adversaries are able to hold their own against the Autobots, almost defeating them until a group of Autobot Headmasters arrive to turn the tide.
Although the Headmasters are a central part to the series, the series introduces several new Transformers, including "The Clones," Sixshot and new versions of Soundwave (Soundblaster) and Blaster (Twincast). Most of the original cast also appear throughout the series, mostly the combiners like the Aerialbots and Stunticons.
Compared to the original series, The Headmasters has an incredibly Japanese flavor. Over the course of the series, the Headmasters evolve into a group of Power Rangers that can detach their heads and turn into vehicles. It's crazy, but incredibly fun if you're into it. Although the series attempts to tell a more solid story than previous seasons, episodes are incredibly bulky and horribly paced. It is not as bad as Dragonball Z, where a conversation can last ten episodes, but there are a couple of throwaway episodes mixed into the 35-episode run.
From the outset, it is clear the writers have somewhere they want to take the show and are in a hurry to get there. By comparison, Rebirth dedicated an entire episode to the Headmaster's origin. Headmasters wraps the entire story up in about a minute. There's also a noticeable push to get rid of familiar characters. Both Galvatron and Optimus are out, and Soundblaster and Twincast are up and running by the end of the first disk. New characters are introduced at a rapid pace, reducing characters like Jazz and Bumblebee (now Goldbug) to background characters.
Not that the changing of the guard is a bad thing. The storytelling might be bad, but it's still fun if you grew up with the series. Most of the plotlines and battles are the type of stuff you probably made up while playing with your Transformers collection. For instance, Combiner battles weren't common in the original series, but happen in nearly every episode of Headmasters. Also, some of the Japanese personalities are much better than the US versions. Sixshot is a silent hired gun in The Rebirth, but is a complete badass in Headmasters. The Headmasters also have more tolerable personalities than their Rebirth counterparts.
This is the first time Headmasters was released in the US (officially, at least), so it is in Japanese with English subtitles. The translations are pretty good, at least when compared to some of the fan subs I found online. Much of the translation has been Westernized, primarily character names. Convoy is called Optimus and so forth. I did, however, notice a couple of glaring spelling and grammatical errors in the subtitles.
There are few questions as to who Transformers: The Japanese Collection - Headmasters is meant for - hardcore Transformers fans. Although newer fans brought up on more recent series, like Transformers: Animated or even Armada might enjoy some of what Headmasters has to offer, the bulky plotlines and flat action may disappoint.