Battle Spirits Saikyo Ginga Ultimate Zero is the latest season of the Battle Spirits anime, following Battle Spirits Sword Eyes. It premiered September 22, 2013 on the usual TV Asahi timeslot. Once again, the series has been re-booted with a new setting and a new cast of characters. This time, it takes place in space.The story features a boy named Rei, who is a Card Quester. Meaning, he's a treasure hunter in space. When he battles, he transforms into the mysterious card battler Zero, and his personality becomes a bit different depending on which color deck he uses. As an obstacle for him, there's also a guild trying to conquer space.
Action Girl: Eris and her crew of space pirates. Oddly, this is averted with Laila, who's just been The Chick so far.
Amnesiac Hero: Rei. The extent of how much he does remember is not yet clear, but he doesn't know how he got Ultimate-Siegfried and Ultimate-Odin.
Art Evolution: The CG in this series is probably the best out of all Battle Spirits seasons.
Art Shift: Shifts to CG during battles, like all previous series.
Duels Decide Everything: This time, it's more incorporated into the plot. The rule of Galactic Battle Spirits says that the players have to wager something of equal value and the loser must give what they offered to the winner.
Elemental Hair: Rei gets this when he battles. His hair turns red when using fire-based red cards, and white when using icy white cards. Likewise, this happens with his green deck.
Miroku is one to Zazie in Brave. They're both masked white-haired villains with an alter ego, not to mention massive trolls. Both try to summon an Ophiuchus card and the process involves sacrificing their own supposed allies. Miroku even imitates Zazie's battle style.
Hair-Trigger Temper: Laila seems to get mad pretty easily. Of course, it doesn't really help how lax Rei seems to be about everything.
Hot-Blooded: When Rei uses red and becomes Zero the Burning, his personality turns to this.
Invincible Hero: Though all Battle Spirits heroes tend to win most of their battles, Zero trashes supposedly-powerful enemies easily, with his ultimate decks. He even manages to beat Kiriga on his first try. No previous Battle Spirits protagonist has managed to beat the rival in one go.
That is, until he is defeated by Kiriga after the latter obtains a White Ultimate, and pulls off the first ever "Guard" (a card discarded by an Ultimate Trigger has a higher cost then the Ultimate, so nothing happens) in the series, he ends up losing Ultimate Odin as well.
Interface Spoiler: Mugen's upgraded form, Mugendragon, has a cost reduction 4, comprising of 2 green spirits, and 2 purple ones, which means it's possible that Rei will obtain a Purple deck in the future.
Which happens in episode 17.
Lighter and Softer: Than Sword Eyes. But not as much as the first episode might make you think.
Meaningful Name: Rei means zero, which is why his alternate personas are named Zero.
Shout-Out: Ultimate Zero has some similarities to Kaiketsu Zubat, of all things; everything is inexplicably western (it being set in space notwithstanding), the hero routinely helps those in need, and he calls himself number one a lot.
All of the Ultimates are based on spirits from the previous Battle Spirits series. In particular, the Tri-Dragon-Deity Ultimates are based on the final ace cards from Gekiha Dan, Brave, and judging by the pattern and Eris' Tri-Dragon-Deity's silhouette, Heroes.
When Rei summons Ultimate-Siegwurm-Nova, the summoning sequence is a very slightly altered version of Siegwurm-Nova's summoning sequence from Gekiha Dan and Brave.
Similarly, when Kiriga summons Ultimate-Sagitto-Apollodragon, the summoning sequence is a direct reference to Sagitto-Apollodragon's from Brave, not to mention the use of Sagitto-Apollodragon's Leitmotif.
Spoiler Opening: It reveals that Rei will use a green deck, as well as his expected red and white ones. The second opening also spoils that Rei will eventually gain a yellow Ultimate, and by extension, a yellow deck via the reveal of a yellow Rei